In this paper we evidenced a broadband transmission from middle infrared to radio spectrum and a band-pass transmission in far infrared based on a sandwich grating structure, which consists a dielectric grating and two metallic covering layers on the top and bottom side of it. It indicates that broadband polarizer or band-pass filter can be inspired from the structure. As a polarizer, the extinction ratio is about 50dB in middle infrared which increases as the wavelength increases; over 90% transmittance for TM polarized light can be maintained from middle infrared to radio spectrum, which doesn’t degrade for incident angle from 0° to 60° . As a band-pass filter working in far infrared region, the resonant transmission peak can be tuned by either varying the thicknesses of the dielectric grating layer or of the metallic coverings. When the resonant transmission peak is tuned from shorter to longer wavelength by increasing the thickness of dielectric grating, the peak transmittance is increased from 61% to 93%, with full width at half maximum (FWHM) bandwidth increases from 13% to 20%. Besides, in order to achieve high peak transmission, the thickness of metallic coverings should be optimized. In consideration of physical mechanism, the step-boosted characteristic of broadband transmission is contributed by the first-order Fabry-Perot (FP)-like cavity resonance supported in the dielectric grating layer along the horizontal direction, while the band-pass transmission is a hybridization resonant mode of the first order FP-like cavity resonance along the horizontal direction and the first-order FP-like cavity resonance along the vertical direction supported in the dielectric grating layer.
DFB LDs are key components in DWDM optical network. Now they are very expensive because the
feedback grating period has to be controlled with very high accuracy and EBL is currently the most
popular solution. We propose a high throughput, low cost NIL process based on a large stamp fabricated
by SFIL and soft stamp pattern transfer method. DFB chips on 30mm*30mm area were manufactured
with both good uniformity and performance. 13 ITU channels from 1540nm to 1560nm of 200GHz space
are made. Our results show NIL has high potential to become another popular technology for DFB LD
production, this cost effective and high efficiency manufacture solution may yield a significant impact to
the future optical communication industry development.
A single device which can demodulate both DPSK and DQPSK formats by simply rotating a quarter-wave plate
is proposed in this paper. Through introducing LC phase retarder and polarization-dependent phase
compensation, fast tuning time of 50ms and low PDFS of less than 300MHz are successfully realized.
The theoretical model considering nonlinear effects in the external cavity semiconductor laser with sampled fiber grating
has been presented. Such effects are including the asymmetric side mode suppression ratio (SMSR) or power
characteristics, and hysteresis phenomena. This theoretical model is based on the transmission line theory on compound
cavity. The parameters of the laser, e.g. active section length and phase section length, have been optimized to suppress
such nonlinear effects, which makes the device control simple and reliable, while the performances such as 16nm tuning
range, 40dB SMSR, 8.5mW output power can be maintained.
It is well known that the thermal expansion coefficient of the cladding layer can significantly influence the stress induced
birefringence in arrayed waveguide gratings. For the first time, the so-called cladding layer is divided to two parts, i.e.
upper cladding and interlayer. The effects of the thermal expansion coefficient, the Young's modulus and the Poisson's
ratio of the interlayer, the upper cladding layer and the buffer layer on thermal stresses in buried channel silica-on-silicon
optical waveguide cores are studied by use of finite element simulation. The results show that the interlayer between
waveguide cores plays the most important role in determining thermal stresses of waveguide cores. The influences of the
upper cladding layer and the buffer layer are small, though the former affects slightly larger than the later. By adjusting
the thermal expansion coefficient of the interlayer instead of the cladding layer, it is faster to minimize the stress induced
birefringence, and the thermal stresses around waveguide cores are almost symmetry. It is also shown that the thermal
stress effects of the thermal expansion coefficient and the Poisson's ratio on the cladding layer can be considered as
linear superposition of those on the interlayer and the upper cladding layer. However, this conclusion is unsuitable for
Young's modulus because of big coupling effect when the thermal expansion coefficient of the interlayer is large.
Thermal stress effects on the mode field characteristics of arrayed waveguides are studied precisely by finite element method (FEM) with plain strain model. The amplitudes of Ex and Ey are comparable for the Ex11 mode and the Ey11 mode in a homogeneous and isotropic optical channel waveguide. Considering the elasto-optic effect, the refractive indices are inhomogeneous and anisotropic. It is shown that the amplitude of Ey for the Ex11 mode and that of Ex for the Ey11 mode are much smaller than the other electric field components. The simplest method to apply thermal stress is to place a stress plate on the arrayed waveguides. It is shown that the effective indices of the two modes, especially the Ey11 mode, can be tuned by stress plates with different thickness. The order of magnitude of tune range is 10-4 whereas the material of plate is aluminum. The effective indices can be increased by attaching an aluminum plate with appropriate thickness under arrayed waveguides, and will be decreased whatever the thickness of the plate is set if attached over arrayed waveguides. However, the stress plate has small effect on the optical mode fields.
Analytical solutions are very useful to understand influence factors in the central wavelength temperature sensitivity of
AWGs (arrayed waveguide gratings) and convenient to be used in preliminary design. In this paper, the elastic multilayer
theory and stress concentration effect are combined to estimate thermal stresses in arrayed waveguides. Effective indices
and their temperature coefficients are estimated by use of effective index method. The effects of material properties on
temperature sensitivity in AWGs are completely studied. It is theoretically demonstrated that athermal AWGs can be
obtained by choosing proper material with negative TEC (thermal expansion coefficient) for the substrate. Subsequently,
the theory is extended to study the modified AWGs with a stress plate attached on the bottom, top, or both sides of
arrayed waveguides. It is shown that the temperature sensitivity can be controlled effectively by stress plates with
different TECs. After attaching a plastic plate on the bottom, the temperature sensitivity of central wavelength can be
reduced to -0.003 pm/K for TE mode and 3 pm/K for TM mode, respectively, whereas the thickness is 0.83mm.
Based on a new metal-wire nano-grating which we suggested recently, a number of optical devices
designs are discussed in this paper. The new metal-wire nano-grating consisted of a series of fine parallel
metallic lines embedded in substrate. The unique property of this embedded grating is that it can be adhered
with other optical elements arbitrarily and can endure any physical and chemical impact on trial due to the
steady homogeneity upper cladding layer. The basic structure of these designs employs four pieces of the
artificial material mentioned above. The two pieces at left side work as PBS. The other two pieces at right side
work as PBC. When we insert one variable LC (liquid crystal) polarization rotator unit between the PBS and
PBC. It could work as an essential 1x2 switch. If the voltage applied on the LC unit is not big enough for 90°
rotation, It could work as an essential 1x2 VPS (variable power splitter). Obviously, when we only deploy one
input and one output, this is an essential VOA (variable optical attenuator). When we insert one interleaver core
between the PBS and PBC, plus two waveplates among the light path, it could works as an interleaver. When
we insert one half waveplate and one Farady rotator, between the PBS and PBC, it could works as a circulator.
We have actually built a prototype of 1x2 VPS (variable power splitter) device, and the performance meets
most of the engineering application requirements.
According to the tilted incidence characteristics of thin film narrowband interference filter, the stack of four cavities angle-tuned narrowband filter with low polarization dependent loss is designed. Using this kind fo angle-tuned thin film filter, one new structure of three-port tunable filter is developed. The experimental results show that its tunable range is at about 20nm.
A new polarization beam splitter/combiner is realized as a one dimensional metal grating structure with periods less than the wavelength; one polarization paralleled to the gratings will be reflected while the orthogonal polarization will be transmitted. We fabricate metal-stripe gratings on glass substrate using E-beam nanolithography technique and reactive ion etching process. A detail investigation of the polarization effect at 1550nm wavelength is carried out with theory analyze and experimental results. The polarization beam splitter has uniform performance with wide variations in the angle of incidence and has low insertion loss, high polarization extinction ratios both the reflected and the transmitted beams.
A new intelligent EDFA design for metropolitan optical networks is proposed. It integrates a post-amplifier and a pre-amplifier function within one module. Only one pump laser, the gain resource could be tunable deployed between the forward and backward directions. In other word, all pump power will be used high efficiently. To demonstrate the super-flexibility of this EDFA, there are a few application cases are described, including the ring and mesh networks situation.
Cr:LiCaAlF6 crystal was grown by modified Bridgman method. The growing process was described in detail. The distribution of Cr along the crystal growth direction was measured and the results showed that the segregation coefficient of Cr is less than 1 under this condition.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
INSTITUTIONAL Select your institution to access the SPIE Digital Library.
PERSONAL Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.