We designed and constructed two novel fiber optic devices that have never been revealed before. One is a wavelength-selective optical router, and the other is a wavelength-selective retroreflector with a bypass fiber channel. They find usefulness in many applications, especially in fiber amplifier, fiber-optic communication, and fiber sensing. To prove their effectiveness, we built a single-stage, two-pass fiber amplifier system composed of these two components. The fiber amplifier yielded an unprecedent 47 dB gain with less than - 23 dB amplified spontaneous emission. The amplifier also possesses a very wide input signal dynamic range and very high output saturation limit. It can be operated in either CW mode or pulse modes.
We developed a high power and high efficiency 1.55 μm fiber laser for eye-safe autonomous driving lidars. A drive current directly modulated DFB laser provides a seed pulse selectable from 2 ns to 10 ns. A high gain (47 dB), low ASE noise (-23 dB), and cladding-pumped multi-pass fiber amplifier is designed and used as the power amplifier. The laser can deliver laser pulses from 80 kHz to 10 MHz with peak powers greater than 5 kW, and pulse energy more than 10 uJ with a single output mode of M2 = 1.05. The laser works in -40 °C to approximately 105 °C environment temperature range with total consumed electrical power ⪅10 W.
We report the latest development of a high power conductively cooled laser module using a novel design approach. The laser bar is directly bonded to two heatsinks in a sandwich configuration without employing submounts as buffers for stress relief caused by CTE mismatch. Simulations were performed to aid the laser module design. The accuracy of the simulations was verified by experimental tests on the laser modules. Production data were collected and used to determine the key performance parameters, statistical distribution, lifetime, and failure mechanism. The laser module thermal rollover could reach 480W at 500A drive current under CW running mode. Furthermore, it could continuously operate under a harsh-hard pulse driving condition at 300A drive current with 300ms pulse width and 1Hz repetition rate.
High power diode laser systems with homogenized intensity distribution have been widely used in laser annealing, cladding and surface heating. New applications such as semiconductor wafer annealing prefer adjustable laser beam size for process optimization, especially during process development stage. Here we report a development of a diode laser system with an adjustable beam size and highly uniform line beam intensity. Beam size in two dimensions perpendicular to its propagation direction can be adjusted independently with higher than 97% intensity uniformity in length dimension. The beam width is adjustable from 60 to 90um (FWHM) and the beam length is adjustable from 11mm to 12mm (FWHM). The output power can reach 1500W at 808nm wavelength with a power density reaches ~170KW/cm2. Detailed misalignment sensitivities of the Micro-Lens Arrays (MLAs), with respect to the lateral position, the rotating angle, and the distance between the two MLAs are studied. Beam back reflection isolation is also considered in the design to accommodate for high reflectivity materials processing. This new laser system can adapt to the requirement of different beam size quickly and precisely by simply adjusting the lens group position, without interrupting production process and increasing manufacturing cost.
We developed model and unveiled the mechanism of the large wavelength-dependent attenuation (WDA) that has been hindering the development of tilting-mirror MEMS VOA. We developed a new tilting-mirror VOA with low WDA of <0.1dB at 20dB attenuation.
KEYWORDS: Signal analyzers, Distortion, Sensors, Modulation, Signal detection, Fiber to the x, PIN photodiodes, Video, Electronic filtering, Interference (communication)
We have designed and fabricated PIN photodiode based ROSA used for FTTX applications. The critical nonlinearity parameters of Inter-modulation Distortion (IMD) were measured by two RF modulated light sources near 1550nm wavelength channels. A cost effective measuring system with narrow pass band filter was set up and some procedures were utilized for determining the low level signals of IMD. Obtained test results were used in real time to guide packaging process to achieve best receiver performance.
Reconfigurable optical add/drop multiplexer (ROADM) is a next generation critical component that facilitates the
network system evolution from a point-to-point transmission-oriented structure to an all-optical, wavelength-flexible,
dynamic network. ROADM enables flexible removal and insertion of WDM channels at either a head-end or
intermediate nodes-making it possible for true network provisioning and reconfiguration.
We will review the pros and cons of each of the techniques for tunable OADM, from their operating principles to their
practical implementations with special emphasis on two approaches: a TTF based three-port tunable filter as a basic
one-channel tunable add/drop multipexer and a full-scale, MEMS mirror array based 80-channel reconfigurable OADM
subsystem. Comparative laboratory experimental results with theoretical calculations are presented.
Reconfigurable Add/drop Multiplexer (ROADM) is a broad definition of a functionally reconfigurable filtering device for dynamic networking. We focus on a class of ROADM architecture that allows scalability of wavelength channels, add/drop port counts as well as functional capability of integrating variable attenuation and monitoring elements. We demonstrate the proposed concepts of integrating a ROADM with a variable optical attenuator and a performance monitor array.
High intensity nonresonant multiphoton ionization has been used in conjunction with time-of-flight mass spectrometry to perform highly sensitive, quantitative, chemical analysis. To achieve quantification of all elements simultaneously and obtain uniform detection efficiencies, all species, regardless of ionization potentials, should be saturated in a single, well-defined volume. To aid in this analysis, 3D potentials intensity distributions of high power laser beams were imaged at a nd near their focus. The cross-sectional intensity distributions of the fundamental and higher order harmonics of a 35-ps Nd:YAG laser beam showed near Gaussian profiles. For nonresonant multiphoton ionization of sputtered or gaseous atoms and molecules, high laser beam quality combined with high power density led not only to photo-ionization saturation of species with quite different ionization potentials, but also to sharply defined ionization volumes. Experiments were performed on the nonresonant multiphoton ionization of species from solid samples and from gaseous samples using well-characterized, high intensity laser beams. The result, driving relative sensitivity factors almost to unity, demonstrate quantitative compositional analysis.
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