Sampled Bragg Gratings Research Articles

Design and Fabrication of Six-Channel Complex-Coupled DFB Quantum Cascade Laser Arrays Based on a Sampled Grating

We designed and fabricated a six-channel complex-coupled distributed feedback (DFB) quantum cascade laser arrays based on a sampled Bragg grating. The six-channel DFB laser arrays exhibit a linear tuning range of 74 nm centered at a wavelength of 7.55 μm at room temperature. Robust single-mode emission with a side mode suppression ratio about 20 dB was observed, even at full power. The used sampled grating and reflectivity coating on the back facet lead to the peak output power varying from 55 to 82mW with a small difference in slope efficiency from 100 to 128mW/A.

Four-Wavelength III-V/SOI Heterogeneous Integrated Laser Based on Sampled Bragg Grating for CWDM

In this paper, we proposed a novel III-V/SOI heterogeneous distributed feedback laser. Stimulated emission generated in a III-V active waveguide modulated by the underneath silicon sampled Bragg grating results in a four-wavelength laser with 18.5-nm wavelength interval targeting for coarse wavelength-division multiplexing. The four wavelengths can be thermally tuned owing to the thermooptic effect of silicon with tuning bandwidth of 2.4 nm.

Tunable Distributed Feedback Quantum Cascade Lasers by a Sampled Bragg Grating

A novel complex-coupled distributed feedback quantum cascade laser emitting around λ ~ 4.7 μm is demonstrated by a sampled Bragg grating (SBG). The key superiorities are to utilize the +1st-order (positive first order) transmission of the SBG for laser single-mode operation, and use conventional holographic exposure combined with the optical photolithography technology to fabricate the sampled grating, which lead to improved flexibility, repeatability, and cost-effectiveness. Selective single-mode lasing with a mean side mode suppression ratio above 20 dB and wavelength coverage range of 87 nm is achieved by changing the sampling period.

Dual current injection tunable SBG semiconductor laser with asymmetric π equivalent phase shift

An asymmetric π equivalent phase shift sampled Bragg grating (SBG) semiconductor, which is consisted of two section with the same length but different sampling duty cycle 0.4 and 0.6, is investigated experimentally. By increasing the two injected currents of the studied laser from 15 mA to 120 mA, the lasing wavelength can be tuned by 2.1 nm. Combining selecting appropriate sampling period, the lasing wavelength of the laser can be tuned to meet the ITU-T standard. Because of high yield and low cost, this type of SBG laser is very beneficial for designing and fabricating monolithically integrated wideband multiwavelength laser array for photonic integrated circuits in next generation fiber-optic system. © 2012 Wiley Periodicals, Inc. Microwave Opt Technol Lett 55:692–696, 2013; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.27357

Fabrication of tailored Bragg gratings by the phase mask dithering/moving technique

The most relevant aspects related to the phase mask dithering/moving method for the fabrication of complex Bragg grating designs are reviewed. Details for experimental implementation of this technique is presented, including theoretical analysis of the calibration functions for the correct dither/displacement. Results from tailored Bragg grating structures fabricated by this method are shown. Apodized Bragg gratings with modeled spatial profiles were implemented, resulting in side mode suppression levels of more than 20 dB in gratings showing transmission filtering level higher than 30 dB. Chirped gratings with the spectral bandwidth up to 4 nm, π-shift and sampled Bragg gratings with equalized peaks equally spaced by 0.8 nm (100 GHz) were also fabricated.

A Special Sampling Structure with an Arbitrary Equivalent-Phase-Shift for Semiconductor Lasers and Multiwavelength Laser Arrays

A method used to introduce an arbitrary equivalent-phase-shift (EPS) into an asymmetric sampled Bragg grating (SBG) is reported. Under the same structural parameters except for the sampling pattern, the asymmetric SBG offers better performance than that of a normal SBG structure for keeping single-longitudinal-mode (SLM) operation. This is because the proposed sampling pattern can suppress the 0th-order light resonance due to the mismatch between the two different grating sections along the whole SBG. This method can be used to design and fabricate semiconductor lasers and multiwavelength laser arrays (MLAs) with the required EPS at high yield and low cost.

Uniform and Sampled Bragg Gratings in SOI Strip Waveguides with Sidewall Corrugations

We have demonstrated uniform and sampled Bragg gratings in silicon-on-insulator strip waveguides with symmetric sidewall corrugations. The fabrication is based on 193-nm deep ultraviolet lithography using a single mask. The measured reflection spectra of sampled gratings exhibit ten usable peaks spaced by 4.2 nm, and show good agreement with theoretical predictions.

Output characteristics of wavelength tunable fiber lasers based on sampled Bragg gratings

A simulation model of the fiber DBR (distributed Bragg reflector) laser with two sampled Bragg gratings (SBGs) as reflectors is established, with which the characteristics of the laser are analyzed in detail. The analysis mainly focuses on the change of the laser output characteristics with the wavelength and reflectivity of the front and back sampled fiber gratings. Because of the multi-channel reflection of SBGs, the side mode of such laser is always very obvious. The method for improving the SMSR(side mode suppression ratio) is suggested. And the wavelength tuning mechanism is also studied. Experiment has been carried out to confirm the analysis.

A Multiexposure Technology for Sampled Bragg Gratings and its Applications in Dual-Wavelength Lasing Generation and OCDMA En/Decoding

In this letter, a multiexposure technology for sampled Bragg gratings is proposed and investigated for the first time. Combined with reconstruction-equivalent-chirp technology, the useless zeroth-order channel can be eliminated and the plusmn1st-order channels can be enhanced significantly. The proposed method is applied experimentally to achieve a dual-wavelength fiber laser and is studied both numerically and experimentally in two ways for the optical code-division multiple access en/decoding system. Its properties may lead to more efficient design and fabrication of grating-based optical devices.

Integrated shadow mask for sampled Bragg gratings in chalcogenide (As_2S_3) planar waveguides

We have developed a new approach for producing high performance sampled Bragg gratings in planar waveguides as a platform for WDM on-chip signal processing in a compact integrated device. Using this method we have successfully integrated a shadow mask directly onto a chalcogenide (As(2)S(3)) waveguide using standard semiconductor processing, eliminating misalignment errors between the mask and waveguide that otherwise occur. Through this integrated mask we demonstrate a very low duty cycle sampled Bragg grating with very narrow rejection peaks and spanning a very broad bandwidth.

Interleaved sampled Bragg gratings with concatenated spectrum

We design and demonstrate interleaved sampled Bragg gratings with concatenated spectrum which produce high channel counts with simple design and fabrication. These gratings can be applied in multichannel filtering, dispersion compensation, and many other functions. The devices were implemented as reduction-photolithographically written anti-symmetric Bragg gratings

Accurate analytical expression for reflection-peak wavelengths of sampled Bragg grating

An analytical expression for calculating the reflection-peak wavelengths of sampled Bragg grating (SBG) is achieved for the first time. The index modulation distribution of SBG is expanded into Fourier series; then the equivalent index modulation and local Bragg period are obtained to derive the expression. Consequently, the introduction of duty cycle and sampling period ensures the accuracy of expression. The phase-matching condition is well explained by the constant phase shift technique. Under this condition, the calculated results based on expression are in good agreement with the numerical reflection spectra obtained by the piecewise uniform method

Sampled Bragg gratings in chalcogenide (As2S3) rib-waveguides

We have written a sampled Bragg grating into a highly photosensitive chalcogenide (As(2)S(3)) rib-waveguide using a scanning Sagnac interferometer. The grating exhibits evenly spaced rejection peaks over a 40 nm bandwidth. We estimate the induced refractive index change of the waveguide to be over 0.03 by matching the measured spectrum to numerical solutions of the coupled mode equations while accounting for an induced chirp. The sampled Bragg grating presented is comparable in strength and bandwidth to the best sampled Bragg gratings obtained to date in silica optical fibre.

Multiwavelength generation in a Raman fiber laser with sampled Bragg grating

Simultaneous continuous-wave multiwavelength operation of a Raman fiber laser is demonstrated with sampled Bragg grating (SBG) at room temperature. The characteristics of multiwavelength fiber ring laser can be easily controlled by adjusting the parameters of the SBG, including the sampling period and the sampling length. In the proposed fiber laser, stable four oscillating wavelengths with 100- and 50-GHz spacing has been achieved, respectively, as well as five oscillating ones with a wavelength spacing of only 25 GHz by varying the sampling period of the SBG.

Spectral self-imaging phenomena in sampled Bragg gratings

We present a detailed study of spectral self-imaging phenomena, namely, integer and fractional Talbot effects, observed in the reflection response of chirped sampled fiber Bragg gratings (C-SFBGs). The basic condition for observing spectral self-imaging effects is first derived heuristically, and an intuitive interpretation of the problem based on the notion of multislit interference is also provided. We then present a rigorous analysis of the spectral self-imaging problem in C-SFBGs, including the formal derivation of the conditions for observing the different spectral Talbot effects. This analysis reveals the existence of new effects, in particular, inverse integer and fractional self-images, which are described here for the first time, to our knowledge. Moreover, we also show that the grating physical parameters need to satisfy additional conditions in order for one to be able to observe spectral self-imaging phenomena in C-SFBGs. We also evaluate the impact of deviations from these ideal conditions on the reflection spectrum of a real device. We confirm our theoretical predictions by using numerical simulations, and we report the first experimental observation of fractional spectral Talbot effects in C-SFBGs. Besides their intrinsic physical interest, the results presented constitute the basis for exploiting the spectral self-imaging effect for practical applications, e.g., to optimize the design of SFBGs for applications requiring periodic comb filters with low in-band dispersion.

Chirped and phase-sampled fiber Bragg grating for tunable DBR fiber laser

Chirped and phase-sampled fiber Bragg gratings are fabricated and used as reflectors in tunable DBR fiber laser for the first time. By controlling the phase of each sampling section, sampled Bragg gratings (SBG) with different channel spacing can be obtained using only a single chirped phase mask. A 30nm-wide tunable Erbium-doped fiber (EDF) laser is designed and experimentally demonstrated by utilizing the vernier effect of two such SBGs with channel spacing of 3.2nm and 3.6nm, respectively. The lasers' output power of different channels is almost identical (difference less than 1dB) within the tunable range.

A Novel Distributed Feedback Fiber Laser Based on Equivalent Phase Shift

A distributed feedback fiber laser employing an equivalent phase shift (EPS) of /spl pi/ is studied theoretically and experimentally for the first time. The EPS is formed through extending one sampling period by 50% in the center of a sampled Bragg grating. An output power of 0.20 mW with sidemode suppression of 67 dB is experimentally observed.

Sampled Bragg grating with desired response in one channel by use of a reconstruction algorithm and equivalent chirp.

The reconstruction algorithm is first applied to a sampled Bragg grating (SBG) with chirp in the sampling period. This method is demonstrated to achieve various profiles of both reflection and group delay within one channel of the SBG. This method has the advantage that the phase mask does not need any chirp, and only submicrometer precision is needed in the fabrication process. Based on this method, a tunable dispersion compensator is fabricated with a tuning range of 300 ps/nm in a flat band of 1 nm.

Tunable Dispersion Compensation in a 10-Gb/s Optical Transmission System by Employing a Novel Tunable Dispersion Compensator

A novel tunable grating exhibiting a linear dispersion in a channel is designed and fabricated for the first time. The equivalent chirp is formed through chirping of the sampling function in a sampled Bragg grating. The sampling period is in the order of millimeter, which can be easily controlled. By employing the tunable grating, the dispersion of 50-km single-mode fiber is completely compensated in a 10-Gb/s transmission with a power penalty of -0.7 dB.

A novel apodization technique of variable duty cycle for sampled grating

A novel apodization technique of writing a sampled Bragg grating is presented for the first time in the paper, which uses an amplitude mask with variable duty cycle and a phase mask. This technique only needs a one-process-exposure instead of two-process-exposure to write an apodized sampled Bragg grating. The numerical simulation has been implemented and the experimental results show that this technique is efficient in reducing the side lobes in the spectrum reflection and the group delay ripples.