This PDF file contains the front matter associated with SPIE Proceedings Volume 8240, including the Title Page, Copyright information, Table of Contents, Introduction, and Conference Committee listing.

The fiber amplification of a gain-switched laser diode and subsequent sum-frequency mixing of the signal with the residual emission from the pump diode of the amplifier is presented as a practical and economical source for a gain-switched distributed feedback (DFB) picosecond laser diode emitting at 1532 nm is coupled into an Erbium-doped fiber amplifier (EDFA) that is core-pumped by a narrowband, single-mode laser diode at 976 nm. The length of the active fiber is optimized for achieving amplification to several watts of puled peak power at 1532 nm, while simultaneously allowing for a significant transmission of the residual pump power after the amplifier. The co-propagating amplified signal pulse at 1532 nm and residual pump at 964 nm provide a convenient geometry for direct fiber coupling into a periodically posed potassium titanyl phosphate (PP-KTP) waveguide for sum-frequency generation (SFG) of picosecond pulses at 596 nm. The variable operation of the seed diode allows for a free-running and triggered configuration over a wide range of repetition operation of the seed diode allows for a free-running and triggered configuration over a wide range of repetition rates for 596 nm pulsed emission from 5 to 80 MHz with pulse energies up to 5 pJ at a pulse duration of sub 122 ps.

An ultrafast fiber MOPA was developed which delivered high average power and rapid and continuous tunability over the range 1035 - 1070 nm. Through FWM in a single PCF, this source generated greater than 30% conversion efficiency to a narrow linewidth signal with tunability from 720 to 880 nm and a corresponding idler tunable from 1370 to 1880 nm. Generation of tunable signal SHG, signal-pump SFG, pump SHG and pump-idler SFG were demonstrated in a single angle tuned BBO crystal. The combined system enabled tunability over large portions of the UV, visible and NIR spectral range from 370 - 1900 nm with a very simple setup. There is scope for power scaling of the source and extending the wavelength coverage.

We present a terahertz source based on difference frequency generation within a laser cavity. Combining the high intracavity intensities of a dual-color vertical external cavity surface emitting laser (VECSEL) with the high nonlinear coefficient of a periodically poled lithium niobate crystal enables the generation of milliwatts of continuous wave terahertz radiation. As the frequency spacing between the two simultaneously oscillating laser lines can be adjusted freely, the entire range of the terahertz gap can be covered. We discuss different approaches for the wavelength control of the dual-color laser sources as well as emission characteristics of the nonlinear crystal. Exemplarily, we chose the frequencies 1.9 THz to characterize the source in term of the beam shape, the linewidth and power scalability. To investigate the emitted THz spectrum, heterodyne detection is employed.

Strong exciton-photon coupling in a high-Q microcavity leads to the formation of two new eigenstates, called excitonpolaritons. We present the quantum dynamics of exciton-polaritons driven by strong few-cycle THz pulses. Our study focuses on an intriguing question of how THz radiation interacts with the strongly coupled light-matter system. We performed THz-pump and optical-probe experiments to answer the question: we observed the time-resolved optical reflectivity of the lower and higher exciton-polariton (LEP and HEP) modes in a QW microcavity in the presence of strong few-cycle THz pulses. In a previous study with a bare QW, a strong THz field tuned to the 1s-to-2p intraexciton transition induced an excitonic Rabi splitting. Since THz radiation interacts only with the excitonic components of exciton-polaritons and has no impact on cavity modes, it is an interesting question how THz radiation drives the excitonpolariton states to higher energy states in the microcavity system. Our study shows that THz radiation resonantly drives the exciton-polariton polarizations giving rise to LEP-to-2p or HEP-to-2p transitions. LEP-to-HEP transition is forbidden because they have the same symmetry. Our experimental and theoretical investigations demonstrate that LEP, HEP, and 2p-exciton states form a three-level Λ system in an optically excited QW microcavity.

Terahertz (THz) radiation via parametric down-conversion of optical pulses in a nonlinear optical crystal is an attractive way to develop frequency tunable THz-wave sources. Therefore, we have focused on developing low-laser-powerpumped THz-wave parametric sources and then successfully demonstrated a synchronously-pumped picosecond THz parametric oscillator (TPO) in pump-enhanced idler-resonant cavity with a bulk 5 mol% MgO-doped lithium niobate (MgO:LN) crystal. In this paper, toward coherent electro-optical (EO) detection of THz waves generated from our synchronously pumped picosecond TPO, we reported time-domain measurements of the THz electric fields using a bowtie- shaped low-temperature grown gallium arsenide (LT-GaAs) photoconductive (PC) antenna as a THz detector. As a result, we obtained temporal waveforms of the THz electric pulses, for the different number of Si-prism couplers, and then found that the radiated THz waves separated multiple unanticipated pulses by use of the arrayed-prism coupling technique. Also, we compared the time-domain system with a Fourier transform Michelson interferometer using a highresistance silicon (Si) beam splitter, from the some viewpoints. The present results reveal great prospects for the realization of THz spectroscopy and imaging applications using our THz-wave source.

Using a tilted-pump-pulse-front scheme, we generate single-cycle terahertz (THz) pulses by optical rectification of femtosecond laser pulses in LiNbO₃. In our THz generation setup, to obtain optimal THz beam characteristics and pumpto- THz conversion efficiency the condition that an image of a grating coincides with a tilted-optical-pulse front is fulfilled. Generated THz pulses have spectra centered at around 1 THz. A designed focusing geometry enables tight focus of the THz beam with a spot size close to the diffraction limit, and the maximum THz electric field of 1.2 MV/cm is obtained. In addition, the nonlinear interactions of GaAs quantum wells with the intense THz pulses have been studied. Here we show that the intense THz pulse, unlike a DC bias, can generate a substantial number of electron-hole pairs forming excitons that emit near-infrared luminescence. The bright luminescence associated with carrier multiplication suggests that the carriers coherently driven by a strong field can efficiently gain enough kinetic energy to induce a series of impact ionizations, which we demonstrate can increase the number of carriers by about three orders of magnitude on picosecond timescale.

Orientation patterned GaAs waveguides for parametric conversion from near to mid-infrared have been fabricated by MOCVD growth on OPGaAs templates. A monolithic OPO cavity was formed by dielectric facet coating. Parametric oscillation characteristics were investigated using a pulsed source tunable in the range of 1.98-2.05μm. Type I and II parametric interactions have been observed, differing in QPM wavelength. OPO threshold power of 7W, using a pulsed pump, and 5.7W using a CW laser was obtained in a 13mm long waveguide of 39μm period. Overall Parametric peak power of 0.6W at pulsed pump peak power of 11.6W was generated at signal & idler wavelengths of 3.6μm & 4.5μm respectively and pump wavelength of 2.015μm. Tuning curves for Type I and type II parametric operation in OPGaAs WGs have been calculated and verified by the measured signal and idler wavelengths.

We employed a 9-mm long periodically-poled KTiOPO4 (PPKTP) crystal with a domain inversion period of 37.8 μm in an optical parametric oscillator (OPO) to generate sub-nanosecond pulses around 2.8 μm. With a 1-cm long OPO cavity in a singly resonant configuration with double pass pumping the OPO threshold was 110 μJ at 1064 nm (1-ns pump pulses at 1064 nm). The maximum idler output energy reached 110 μJ (quantum conversion efficiency of 32.5%). The signal pulse duration (FWHM) was 0.72 ns and the estimated idler pulse duration was 0.76 ns. At room temperature the signal and idler wavelengths were at 1722 and 2786 nm.

The beam quality of the idler output of a 1064 nm pumped OPO based on CdSiP2 is compared for linear and Rotated Image Singly-Resonant Twisted RectAngle (RISTRA) cavities. For similar mirrors and cavity round trip times the RISTRA cavity yielded 64 μJ of idler energy (6.4 mW of average power at 100 Hz) compared to 34 μJ with the linear cavity, at a pump level of 21.5 mJ, roughly two times above threshold. The RISTRA cavity generated a somewhat smoother idler beam spatial profile (characterized by moving a knife-edge) and the intensity in the focus of a 10-cm lens was about 50% higher.

We present a technique increasing the space bandwidth product of a nonlinear image upconversion process used for spectral imaging. The technique exploits the strong dependency of the phase-matching condition in sum frequency generation (SFG) on the angle of propagation of the interacting fields with respect to the optical axis. Appropriate scanning of the phase-match condition (Δk=0) while acquiring images, allow us to perform monochromatic image reconstruction with a significantly increased space bandwidth product. We derive the theory for the image reconstruction process and demonstrate acquisition of images with >10 fold increase in space bandwidth product, i.e. the number of pixel elements, when compared to upconversion of images using fixed phase-match conditions.

We present a quasi-cw laser in vacuum ultraviolet region at megahertz repetition rate. The narrowband pulses generated from an ytterbium-fiber laser system at 33 MHz repetition rate at the central wavelength of 1074 nm is frequency-converted by successive stages of LBO crystals and KBBF crystals. The generated radiation at 153 nm has the shortest wavelength achieved through phase-matched frequency conversion processes in nonlinear optical crystals to our knowledge.

Spectralus presents its progress in development of miniature, highly efficient, and versatile diode-pumped solid-state (DPSS) green laser source, based on a monolithic cavity microchip laser platform. The use of periodically poled MgO-doped Lithium Niobate (PPMgOLN) as the nonlinear frequency doubler together with gain material Nd³⁺:YVO₄ allows obtaining a significant increase in the overall efficiency of the green microchip laser in comparison with other compact green laser source architectures with comparable output power. Originally, this laser source was designed to be part of the miniature and efficient RGB light source for microdisplay-based (LCOS, DLP or similar) mobile projector devices. Recently, we have extended range of operations for our original laser platform. In particular, we demonstrate the following: high peak power (>500mW), high average power (>200mW), broad temperature range of operation (-30°C - 60°C), and low noise CW operation (<0.5% RMS).

Supercontinuum generation in photonics crystal fibers (PCFs) pumped by CW lasers yields high spectral power density and average power. However, such systems require very high pump power and long nonlinear fibers. By on/off modulating the pump diodes of the fiber laser, the relaxation oscillations of the laser can be exploited to enhance the broadening process. The physics behind the supercontinuum generation is investigated by sweeping the fiber length, the zero dispersion wavelength, and the fiber nonlinearity. We show that by applying gain-switching a high average output power of up to 30 W can be maintained and the spectral width can be improved by 90%. The zero dispersion wavelength should be close to but below the pump wavelength to achieve the most visible light. By increasing the nonlinearity the fiber length can be reduced from 100 m to 25 m and the efficiency of visible light generation is improved by more than 200%.

We present experimental results of a single-stage Raman fiber amplifier (RFA) for guide star application. SBS suppression was achieved through the acoustic tailoring of the core of a polarization-maintaining single-mode conventional fiber. The core was also doped for enhanced Raman gain. This fiber was utilized in a counter-pumped amplifier configuration to generate 1178 nm light with a linewidth < 2 MHz for frequency doubling into the D₂ sodium line. Due to the SBS suppressing characteristics of the fiber, the RFA provided 11.2 W of 1178 nm signal when seeded with 15 mW. Application of a thermal gradient allowed for further power scaling leading to 18.3 W. Our measurement of the linewidth at the highest output power indicated no spectral broadening.

Ultra-broadband supercontinuum (SC) at 1-μm wavelength is regarded as diagnostics window in bio-photonics due to its large penetration depth in tissues and less Rayleigh scattering. Dispersive Fourier transform (DFT) is an important technique to realize the high-speed, ultra-fast and high-throughput spectroscopy. Thus, a stable light source with good temporal stability plays an important role in the bio-imaging and spectroscopy applications. We here demonstrate stabilized and enhanced SC generation at 1 μm by a minute continuous-wave (CW) triggering scheme. By introducing a weak CW (~200,000 times weaker than the pump), a significant broadening in the SC bandwidth and an improvement in the temporal stability can be obtained. Over 8 dB gain is achieved in both blue and red edges and the SC spectrum can span from 900 nm to over 1300 nm with the CW trigger. We present the CW-triggered SC capability of enabling highspeed spectroscopy based on DFT at 1 μm. In regards to the performance of DFT, the wavelength-time mapping fluctuation reduced by 50% which is an indication of the improvement of the temporal stability. This triggering scheme allows, for the first time, 1-μm DFT at a spectral acquisition rate of 20 MHz with good temporal stability - paving the way toward realizing practical real-time, ultrafast biomedical spectroscopy and imaging.

Three dimensional Light Bullets (3D-LBs) are the most symmetric solitary waves, being nonlinear optical wavepackets propagating without diffraction nor dispersion. Since their theoretical prediction, 3D-LB's have constituted a challenge in nonlinear science, due to the impossibility to avoid catastrophic collapse in conventional homogeneous nonlinear media. We have recently observed stable 3D-LBs in media with periodically modulated transverse refractive index profile. We found that higher order linear and nonlinear effects force the 3D-LBs to evolve along their propagation path and eventually decay. The evolution and decay mechanism entails spatiotemporal effects, which under certain conditions, leads to superluminally propagating wavepackets.

We report a compact, efficient, high-energy and high-repetition-rate mid-infrared picosecond optical parametric oscillator (OPO) based on a new nonlinear material CdSiP₂. The OPO is synchronously pumped by a master-oscillator power-amplifier system at 1064.1 nm, providing 1-μs-long macro-pulses constituting 8.6 ps micro-pulses at 450 MHz, and can be tuned over 486 nm across 6091-6577 nm, covering the technologically important wavelength range for surgical applications. Using a compact cavity (~30 cm) and a CdSiP₂ crystal, idler macro-pulse energy as high as 1.5 mJ has been obtained at 6275 nm, for an input energy of 30 mJ. The extracted signal pulses have durations of 10.6 ps.

We demonstrate a simple method for spectral broadening and compression of laser pulses at megahertz repetition rates by self-phase modulation in a large mode area (LMA) fiber. In order to avoid the currently limiting factor of damage by self-focusing, we positively chirp the input pulse, which allows coupling of significantly more energy into the fiber, while maintaining the same spectral bandwidth and compression as compared to the Fourier-limited case at lower energy. Using a commercial chirped pulse Ti:Sa oscillator (Femtolasers, Femtosource XL) with 55fs, 400nJ pulses at 5MHz and an LMA fiber with 25μm core diameter, we generate 16fs, 350nJ pulses, which is a factor of 4 more energy than possible with unchirped input pulses. Good stability has been measured over at least 1 hour for the chirped case and unchirped case. Furthermore, with a 5μm core diameter LMA fiber we generated compressed pulses with 6fs and 18nJ output energy. This would allow a carrier-to-envelope phase stabilization of the laser system by external selfstabilization via acoustic difference-frequency modulation. The compact size and its simplicity makes the combination of a chirped pulse oscillator with chirped-fiber-broadening an attractive option for ultrafast spectroscopy at MHz repetition rate.

The achievement of high contrast, high efficiency OPCPA systems has been a long established goal. We achieve close to ~20% conversion in a picosecond OPCPA system. This is now the standard seed for our petawatt pre-amplifier laser system which had a conventional 10⁸ nanosecond gain. We thereby eliminate the need to the first nanosecond gain stage. We achieve a contrast at the 10^-8 level when using the petawatt system in this configuration. We have also demonstrated a second stage of picosecond amplification with an extra gain of >2, maintaining the bandwidth and transform limited nature of the pulses, providing the potential for further improvements.

Amplification of femtosecond pulses using an ultra-narrowband gaseous pulse laser was demonstrated for the first time. A single-shot sub-nanosecond iodine photodissociation laser with a bandwidth of 20 pm was used as a driver in an allstage OPCPA. An externally triggerable OPO tuned to laser line of 1315.24 nm was used in the front end of the iodine laser. Frequency tripled beam at 438 nm was used to pump parametric amplifiers, LBO and KDP crystals. The signal pulses from a Ti:sapphire laser at the central wavelength of 800 nm with a bandwidth of 70 nm (FWHM) were stretched from 12.5 fs to 250 ps and amplified by a factor of 2×10⁸. The amplified pulses of typical bandwidth of 50 nm were compressed down to 27 fs. The output power of 0.5 TW was achieved. An optimized amplifier chain and addition of a third nonlinear crystal would enable to generate femtosecond pulses of several terawatts. The broadband pulses at 800 nm central wavelength were amplified in the KDP crystal for the first time, due to the suitable wavelength of the pump pulses. Availability of large aperture KDP crystals promises the generation of petawatt beam at kJ iodine laser facilities.

We generate broadband mid-infrared frequency combs via degenerate optical parametric oscillation in a subharmonic OPO. This technique efficiently transfers the desirable properties of shorter wavelength mode-locked sources to the mid- IR. Our OPO resonator is a 3m or 4m ring cavity composed of one pair of concave mirrors with R=50mm and four flat mirrors, all but one of which are gold coated with > 99% reflection. A single dielectric mirror is used to introduce the pump (2.05 micron from IMRA America, 75 MHz, 80 fs, 600mW or 1.55 micron from Menlo Systems C-fiber, 100 MHz, 70 fs, 350 mW or 1.56 micron from Toptica Photonics FemtoFiber Pro, 80 MHz, 85 fs, 380 mW). The dielectric mirror is transmissive for the pump and reflective in a 2.5- 4 micron or 3- 6 micron (for 2 micron pump) range. Broadband parametric gain around the 3.1-micron subharmonic is provided by short (0.2-0.5mm) periodically poled lithium niobate (MgO:PPLN) at Brewster angle. Crystals were cut from Crystal Technology Inc. material having QPM period of 34.8 microns for type 0 (e=e+e) phase matching at t=32 deg. C. With the 2-micron pump, orientation patterned gallium arsenide from BAE systems is used as the non-linear material In both systems, the enormous acceptance bandwidth at degeneracy, typical for OPOs with type 0 (or type I) phase-matching, gives broad bandwidth and makes temperature tuning insignificant. Broadband oscillation is achieved when signal/idler are brought into degenerate resonance by fine-tuning the cavity length with a mirror on a piezo stage. Using an 8% reflective pellicle, we outcouple a frequency comb of more than 1000nm bandwidth, centered around 3.1 microns from the Er/PPLN system. A 1mm or 2.5mm thick ZnSe plate at Brewster angle provides 2nd-order group velocity dispersion compensation, improving the OPO bandwidth. The OPO threshold was measured to be < 30mW. When locked, the OPO outputs 60 mW of average power centered at 3.1 microns. With the Tm/OP-GaAs system we achieve octave-spanning output from 3- 6 micron using a mix of YAG and CaF for dispersion compensation and output powers over 30 mW.

Few-cycle pulses offer a wide range of interesting applications, for example in time-resolved studies of ultra-fast phenomena in physics, chemistry and biology. Nonlinear spectral broadening in photonic crystal fibers (PCFs) followed by dispersive compression allows for the generation of extremely short optical pulses. By employing this technique pulse durations of only 5.5 fs (2.4 optical cycles) have been achieved so far. In this contribution we take advantage of SC generation in all-normal dispersion PCF (ANDi PCF), which features only positive group-velocity dispersion across the spectral region of interest. Spectral broadening therefore is dominated by self-phase modulation and optical wave breaking, leading to smooth and highly coherent SC spectra. We show generation of SC spectra covering more than one optical octave around 810 nm central wavelength. Active phase control and spectral shaping were employed to compress the pulses to 3.64 fs (1.3 optical cycles), which is the shortest pulse duration achieved from SC compression in solid core fibers to date. In contrast to other approaches, the presented concept delivers pulses with an excellent temporal pulse quality and can be extended to even larger bandwidths to reach the sub-cycle regime, provided an adequate compressor is employed.

An investigation of the birefringence uniformity of mid-IR non-linear optical crystals has been conducted in an effort to improve the performance of crystals used in OPO converters. This paper discusses the development of an imaging polarimeter operating at 2 μm for the characterization of birefringence uniformity of nonlinear optical crystals for use in mid-IR generation. The spatial distribution of optical in-homogeneity is directly revealed in terms of optical rotation in the polarimeter. The root cause for the optical rotation observed in the polarimeter is discussed in terms of fluctuations in the material birefringence, or excess birefringence. Excess birefringence on the order of ▵n=10^-4 are measured in samples exhibiting the rare occurrence of low birefringence uniformity in our mid-IR nonlinear optical crystals.

We propose and examine single-stack matching-layer enhanced Bragg re ection waveguides as a platform for integrated parametric devices. The proposed designed is asymmetric in geometry, where a multi-layer core is surrounded by a single-layer upper cladding and a lower quarter-wave Bragg mirror. The propagation of the Bragg mode in the new design relies on total internal reection form the upper cladding and Bragg reflectionthe lower periodic cladding. Analytical expressions for modal analysis of TE- and TM-polarized Bragg modes are derived. An Al_xGa_xAs second-harmonic generation device is theoretically examined to highlight nonlinear performance of the new design and it is compared to symmetric phase-matched Bragg reflection waveguides reported to date.

With the development of more powerful lasers for applications, optical limiters and blockers are required for providing human eye and optical sensors protection. We report on passive optical power control devices based on a range of photonic nanostructures, including mainly nanostructures for spatial field localization to enhance optical nonlinearities. We present the two main optical power control mechanisms: blocking and limiting, as well as their corresponding nanoscale phenomena. We propose a dynamic protection to cameras, sensors and the human eye from laser threats.

Praseodymium-ytterbium codoped fluorogermanate nano-structured phosphors for solid-state lighting were synthesized by thermal treatment of precursor glasses. Room temperature luminescence features of praseodymium-ytterbium ions incorporated into low-phonon-energy PbF₂ nanocrystals dispersed into the fluorogermanate glass matrix and excited with near-infrared light emitting diode laser was evaluated. The luminescence spectra exhibited predominant emissions in the 475-500, 520-530, and 600-650 nm regions. White-light emission was observed in ytterbium-sensitized praseodymiumdoped phosphor excited at 980 nm. The dependence of the luminescence emisson intensity upon annealing temperature, and rare-earth concentrations was also evaluated. The results indicated that there exist an optimum annealing temperature and activator ion concentration in order to obtain efficient upconversion emission signals with CIE 1946 chromaticity coordinates within the white-light borderline region. Results indicate that the nanocomposite fluorogermanate glassy phosphor is a promissing novel contender for application in white-light solid-state display technology

Stimulated Brillouin Scattering (SBS) is a nonlinear optical effect that is broadly used for correcting the beam quality of laser beams, their mode control, amplification and phase conjugation. Two factors are essential when it comes to selection of the nonlinear medium for SBS, its efficiency or gain coefficient and safety. For example, a low SBS gain coefficient in the fluorocarbon liquid C8F18 is at least one order of magnitude lower than other nonlinear media, typically limits its application in high-power laser systems. However, highly purified C₈F₁₈ is a very safe and stable nonlinear medium, and in combination with its high optical breakdown threshold, has become attractive for many practical applications. This paper discusses a phase conjugate mirror (PCM) using the SBS effect in C₈F₁₈. A PCM reflectivity of better than 90% has been achieved in an optimized experimental geometry of the incoming beam. The output energy of the phase conjugated pulse linearly increased with the energy of the input pulse beyond a threshold level of about 3.3 mJ. The estimated slope efficiency is about 95%. For weak signal amplification, we have realized greater than 105 amplification with Brillouin enhanced four wave mixing (BEFWM) with an input signal at the level of several nJs. A reflected energy as high as 11 mJ has been achieved with a 400 μJ incoming input signal. Further lowering of the signal energy should result in a higher amplification.

We reported Supercontinuum (SC) generation in standard telecom fiber using picosecond pulses of microchip laser. The pulses width is 700 ps at 1064 nm, using 57 m long of standard fiber, and the spectra extend from 700 to above 1700 nm, some 100 nm further into the visible. The physical processes leading to the formation of the continuum spectrum were studied by monitoring the growth of the SC while increasing the input power. The coupling efficiency of ours experimental setup between the microchip laser and the telecom fiber helped us to obtain this wide spectrum.

In this paper we have numerically investigated the parametric down conversion process in one dimensional-photonic band gap (1D-PBG) structure, which is composed of linear and nonlinear dielectric layers, under four wave mixing phenomena. The nonlinear dielectric layer is material with third-order nonlinear susceptibility χ⁽³⁾. First, we used coupled-mode theory and slowly varying amplitude approximation to derive a complete set of nonlinear coupled mode equations (NLCMEs) for the FWM phenomena. Then, we have solved these NLCMEs by using undepleted pump approximation. We have got the solution for amplitude of signal and idler waves. Finally, we have used these solutions to calculate the down-converted frequency conversion efficiency. We found that the conversion efficiency can be enhanced by increasing the number of periodic layers and χ⁽³⁾ value. Meanwhile, the conversion efficiency is decreased by increasing of phase mismatch (▵k).

All-optical networks introduce the indisputable solution for future networking especially due to discarding slow and power-demanding electronic processing. Ultrafast data communications ultimately head towards all-optical packet data transfer and optical IP routing. In this paper, nonlinear switching techniques are evaluated with respects to particular types of nonlinear fibers with regards to their specific parameters. Optical packet labeling is discussed, considering label allocation between ITU-grid defined data wavelengths. Possible aspects of a highly-nonlinear fiber, untapered and tapered chalcogenide fibers integration into the optical switch were investigated both theoretically and experimentally.

Recently, we have tried to develop a continuous wave (CW), tunable, and ultraviolet (UV) coherent light source through sum-frequency generation (SFG) using a BBO nonlinear crystal with a two-stage frequency-conversion system using two different external cavities for the enhancement of CW lights. In the first stage, we obtained the 532-nm light with the second harmonic generation (SHG) of the 1064-nm light. A bow-tie external cavity incorporating four mirrors, whose cavity length was controlled by the frequency stabilization method proposed by Hänsch and Couillaud, was employed there. In the second stage, to generate the 312-nm light, we demonstrated doubly resonant sum frequency generation of the 532-nm light from the first-stage and the 754-nm light from a single-frequency CW Ti:Sapphire laser. Considering a nonlinear coefficient, it should be preferable to use a BiBO crystal for high-efficient SFG, but the 312-nm light might be absorbed by the BiBO crystal. Therefore, we chose a BBO as a nonlinear crystal to avoid the absorption of the 312-nm light.

A terahertz (THz) parametric oscillator (TPO), which was based on the optical parametric process, in a doubly-resonant external enhancement cavity synchronously-pumped by a mode-locked picosecond Ti:sapphire laser with the center wavelength of 780 nm and the average output power of 850 mW, was built. Our TPO cavity including four mirrors and a 5 mol% MgO-doped LiNbO₃ (MgO:LN) crystal with Si-prism couplers for the output coupling of the THz wave was designed so as to circulate both pump and idler waves in the same cavity simultaneously. Furthermore, we utilized a Hänsch-Couillaud method to stabilize the cavity. As a result, we developed an easily and continuously tunable picosecond TPO by changing the noncollinear phase-matching condition. The tunable wavelength range of the idler wave was from 782 to 787 nm, which corresponded to the THz frequency range from 1.0 to 3.4 THz according to the law of energy conservation. In addition, the measured angle between the pump and idler waves, which varied from 0.6 to 2.5 degrees, showed a good agreement with the theoretical calculation of the noncollinear phase-matching condition in all the above tuning range.

Upconversion and nonlinear optical properties of the glasses have been studied. Optical band gap value 3.52eV calculated from the linear optical absorption measurement of the glass. The green upconversion emission of Er3+ ions from ²H_11/2 → ⁴I_15/2 to ⁴S_3/2 → ⁴I_15/2 transitions have been measured under femtosecond laser excitation of 100fs pulse at 80Mhz repetition at 800nm wavelength .Upcoversion emission intensity variation was observed on laser pump power from 50mW to 100mW and confirmed that two photon processes are involved at lower pump power . The nonlinear absorption has been measured by z-scan measurements using 100fs laser pulse and optical nonlinearity of the glass was calculated. The relationship between the nonlinear optical properties and the glass structures estimated by Raman spectroscopy was discussed. The nonlinearity of these TWL glasses increased as the stretching Raman band of TeO4increased, while the stretching band of TeO₃ decreased. This indicate that amount of TeO₄ units was deeply related to the third order non-linearity.

Supercontinuum generation is being widely studied due to its applications in communications, medicine and metrology. Usually, special fibers, such as photonic crystal fibers and dispersion-shifted fiber, have been utilized. However, there is few information about the potential use of standard fiber with this purpose, which shows some advantages: low cost and availability. In this work, the influence of losses due to induced macrobends on the supercontinuum generation using standard fiber was studied. The losses were introduced by wrapping 30 m in length of standard fiber on cylinders with different diameter, a nanosecond microchip laser and 1064 nm of wavelength were employed. The continuum was recorded at the fiber output by using an optical spectrum analyzer and its dynamics was analyzed by tuning the launched power. In a first stage, the fiber was used without bends generating strong firs-order Raman Stokes and a supercontinuum spectrum of 636 nm. When the fiber was wrapped in a cylinder of 0.9 cm of diameter to induce macrobends, the Raman Stokes of high order were attenuated and the output spectrum was reduced to 240 nm. Also, a peak pulse was observed, around 1030 nm, that means new frequencies were generated in the near infrared region. Thus, induced macrobends affect the supercontinuum broadening.

We have developed a mathematical/numerical framework based on computational transition modules and measured ultrafast laser light propagating through nonlinear materials. The numerical framework can be applied to a broad set of photo-activated materials and lasers, and can optimize photo-physical parameters in multi-photon absorbers. Two photon (TPA) processes are particularly useful in many applications including fluorescence imaging, optical data storage, micro-fabrication, and nanostructured quantum dots for optical limiters. Laser transmission measurements of the organic molecular chromophore, AF455-known TPA material-were taken with a 175 fs, λ₀=780nm, plane-polarized light pulses from Ti:S regenerative amplifier into a 5.1mm thick PMMA slab doped with the chromophore. The range of input energies (intensities) in this experiment was 0.01μJ (0.97 GW/cm²) to 25 μJ (2.4 x10³ GW/cm²). Experiments showed that for intensities beyond several μJ, the material did not saturate as predicted by traditional theory. We included excited-state absorption (ESA), as demonstrated by the absorption spectrum, which still could not account for the deviation. To understand this result we used our framework to show that an unexpected/unknown higher energy level was being populated. We calculated the entire experimental curve from 0.01μJ (0.97 GW/cm²) to 25 μJ (2.4 x10³ GW/cm²) and found excellent agreement with the experimental data.

Both a high level of developing the spatially spot-like and one-dimensional input devices and the flexibility of a design inherent in two-dimensional optical systems with similar modulating components make it possible to realize various high-bit-rate opto-electronic processors. This is why a one-dimension acousto-optic technique has been involved in data processing and its modeling based on the algorithm of triple product correlations. Practically, triple product correlations originate within an optical scheme including the modulated light source, representing the first input port, and two wideaperture acousto-optical cells forming two other input ports. Due to specifically constructed lens system, initially modulated light beam is crossing sequentially the apertures of acousto-optical cells oriented at right angle to each other. Finally, a CCD-matrix integrates the received optical signal with respect to time and registers the resulting triple product correlations. In a view of arranging similar acousto-optical processor for modeling triple product correlations, we characterize a novel version of the acousto-optical cells exploiting now tellurium-dioxide crystals. Together with this, potential performances of the progressed design for similar processor are estimated as well.

Periodic inversion of spontaneous polarization in a ferroelectric substrate has realized quasi phase matching (QPM) and thereby revolutionized nonlinear optics. In this paper, we report on the heat influence on the frequency conversion in birefringence phase matching (BPM) by use of BaB₂O₄ (BBO) crystals as preparatory for efficient generation of the second harmonics (SHs) by QPM we suggest. Indeed, QPM is achieved normally by polarization inversion, but we suggest the periodic step structure to achieve QPM. Polarization inversion is generally formed by superimposed voltage. However, the shorter wavelength region is, the shorter inversion cycle is. Therefore, if the vacuum ultraviolet (VUV) region is treated, it becomes more difficult to form periodic inversion and the accuracy is more necessary. Accordingly, it is necessary to consider the influence of crystal's heat, caused by absorption of laser, which affects frequency conversion. We discuss validity of analytical approach about crystal's heat and frequency conversion by comparing between both results of experiment and simulation with BBO crystals.

In this paper, we drew a 500 m-long PCF taper directly on the industry drawing tower. The fiber taper has a uniform cross-section structure with OD from 170 μm to 70 μm, and demonstrates very good beam quality. The optical attenuation of PCF taper was measured. The optical attenuation is ~5 dB/km near 1200 nm, but the water absorption peak around 1400 nm and the attenuation beyond 1600 nm are still large. The zero dispersion wavelength (ZDW) was calculated to be ~1090 nm at the taper input end, and shifted to ~870 nm at the taper output end. The PCF taper was pumped with a picosecond laser source at wavelength of 1064 nm, and generated 200 mW output power of SC covering from ~450 nm to 1600 nm.

Rather specific types of light diffraction in the condensed matters are analyzed theoretically, so that in fact a set of processes conditioned by a multi-phonon light scattering in the Bragg regime is under investigation. Besides of their scientific novelty, studying these phenomena promises real progress in applications, because practical exploiting of the m - phonon processes in frontier schemes for the acousto-optical spectrum analysis of both optical and radio-signals leads potentially to improving the frequency and/or spectral resolution of the corresponding analyzers by almost m - times. With this in mind, the wave-based description, the corpuscular approach as well as the quantum interpretation of acousto-optical interaction are used here to characterize various aspects related to improving the expected resolution of acousto-optical devices exploiting a multi-phonon light scattering. In so doing, the quantity of orders under consideration is limited by number N ≤ 4 , which is still hopefully possible to be achieved experimentally in Bragg regime. Additionally, a brief description of a multi-order light scattering by usual thin diffraction grating is presented in the appendix for the convenience of its physical comparison with the results obtained for acousto-optics.