Yating Zhou

Experimental demonstration of eight-wavelength distributed feedback semiconductor laser array using equivalent phase shift

An eight-wavelength distributed feedback semiconductor laser array with λ/4 equivalent phase shift based on reconstruction-equivalent-chirp technique was demonstrated. It shows very good linearity in lasing wavelengths with its deviation from -0.22 to 0.20 nm. The threshold currents are between 19 and 24 mA. The side-mode suppression ratios are all larger than 40 dB under the bias currents of 70 mA. The slope efficiencies at room temperature are all about 0.4 W/A. The grating was fabricated only by common holographic exposure and an additional micrometer-level conventional photolithography, which results in a low cost.

Study of the Multiwavelength DFB Semiconductor Laser Array Based on the Reconstruction-Equivalent-Chirp Technique

A detailed theoretical analysis of the lasing wavelength precision of the DFB laser array based on a reconstruction-equivalent-chirp (REC) technique is presented. Experimental results of the eight-wavelength DFB laser array with equivalent π phase shift (π-EPS) and four-wavelength DFB laser array with equivalent three shifts are also given. High lasing wavelength precision was obtained. This paper demonstrates that the REC technique is a promising way for fabricating the multiwavelength DFB laser array with low cost and high yield.

Experimental demonstration of the three phase shifted DFB semiconductor laser based on Reconstruction-Equivalent-Chirp technique.

A three phase shifted (3PS) distributed feedback (DFB) semiconductor laser based on Reconstruction-Equivalent-Chirp (REC) technique is experimentally demonstrated for the first time. The simulation results show that the performances of the equivalent 3PS DFB semiconductor laser are nearly the same as that of the true 3PS laser. However, it only changes the μm-level sampling structures but the seed grating is uniform. So, its cost of fabrication is low. The measurement results exhibit its good single longitudinal mode (SLM) operation even at high bias current and surrounding temperature.

A novel concavely apodized DFB semiconductor laser using common holographic exposure

A novel concavely apodized (CA) distributed feedback (DFB) semiconductor laser was theoretically analyzed and experimentally demonstrated. The CA grating profile is equivalently realized by changing the duty cycle of the sampling structure along the cavity in the middle of which an equivalent phase shift is also inserted. Because the basic grating (seed grating) is uniform, only a common holographic exposure and a µm-level photolithography are required. Therefore, the fabrication cost is highly reduced compared with the true CA grating whose index modulation continuously changes along the cavity. The experimental results show that the laser has good single longitudinal mode operation.

An Anti-Symmetric-Sample Grating Structure for Improving the Reconstruction-Equivalent-Chirp Technology

This letter presents a novel sampled grating structure for improving reconstruction-equivalent-chirp (REC) technology. The proposed structure has uniform seed grating but with the anti-symmetric-sample structure. It has been found that in such a structure, the wavelengths of the ±1st channels can be both blue-shifted more than 40 nm, but the wavelength of the 0th channel is not changed. When the +1st channel is used as the working channel, the wavelength spacing between the +1st channel and the 0th channel is increased by more than 40 nm. Such a phenomenon will be sure to increase the performance and working bandwidth of the REC-based components such as the REC-based distributed-feedback (DFB) laser/laser array.

Asymmetrical sampling structure to improve the single-longitudinal-mode property based on reconstruction-equivalent-chirp technology

We propose a special asymmetric sampling structure based on reconstruction-equivalent-chirp technology to effectively suppress the side mode oscillation in the zeroth channel in a sampled Bragg grating semiconductor laser, which improves greatly the single-longitudinal mode (SLM) oscillation capability of the laser. A numerical simulation is performed. The proposed structure guarantees a normalized threshold gain margin between the main mode and the side mode larger than 0.3. A high side-mode suppression ratio is also observed. The proposed method would be of great importance for the fabrication of high-performance and wideband multiwavelength laser arrays with each laser operating in SLM.

Multisection DFB Tunable Laser Based on REC Technique and Tuning by Injection Current

Based on the reconstruction-equivalent-chirp technique and tuning only by the injection current, a multisection DFB tunable laser is demonstrated experimentally. At the temperature of 20°C, each laser can be tuned at about 3.4-3.6 nm with a side-mode suppressing ratio (SMSR) of over 35 dB from 30 to 170 mA, and the tuning speed is about 10-30 ms, which is much faster than that by the thermoelectric cooler. The results may help to realize very low cost tunable lasers in the future.

Numerical Study of an Asymmetric Equivalent

Based on reconstruction-equivalent-chirp technology, an equivalent λ/4 phase shift was introduced into the center of an asymmetric sampled Bragg grating semiconductor laser that had two sections of the same lengths but different effective refractive indices. This structure could suppress the zeroth-order channel lasing effectively and enable the laser to operate in a single longitudinal mode with high stability. Such a method can also be used to fabricate a high-quality multiwavelength laser array for enhancing the yield efficiently at reduced cost.

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A laser array, which is consisted of 56 π equivalent phase shift (EPS) sampled Bragg grating (SBG) semiconductor laser, is experimentally investigated. The experimental results show the influence of the sampling duty cycle fabrication error on the lasing wavelength of an SBG semiconductor laser can be ignored.

Phase Shift Semiconductor Laser for Use in Laser Arrays

We designed and experimentally studied a sampled Bragg grating semiconductor laser with π equivalent phase shift (EPS) and three equally separated electrodes. When the central electrode is injected different current from the other electrodes, a distributed phase shift (DPS) can be introduced into the studied laser. By changing the injection current ratio into three electrodes, the DPS can be controlled and then the lasing wavelength can be tuned while the laser keeps single longitudinal mode operation.