Jingsi Li

Experimental demonstration of distributed feedback semiconductor lasers based on reconstruction-equivalent-chirp technology

In this paper we report, to the best of our knowledge, the first experimental realization of distributed feedback (DFB) semiconductor lasers based on reconstruction-equivalent-chirp (REC) technology. Lasers with different lasing wavelengths are achieved simultaneously on one chip, which shows a potential for the REC technology in combination with the photonic integrated circuits (PIC) technology to be a possible method for monolithic integration, in that its fabrication is as powerful as electron beam technology and the cost and time-consuming are almost the same as standard holographic technology.

High channel count and high precision channel spacing multi-wavelength laser array for future PICs

Multi-wavelength semiconductor laser arrays (MLAs) have wide applications in wavelength multiplexing division (WDM) networks. In spite of their tremendous potential, adoption of the MLA has been hampered by a number of issues, particularly wavelength precision and fabrication cost. In this paper, we report high channel count MLAs in which the wavelengths of each channel can be determined precisely through low-cost standard μm-level photolithography/holographic lithography and the reconstruction-equivalent-chirp (REC) technique. 60-wavelength MLAs with good wavelength spacing uniformity have been demonstrated experimentally, in which nearly 83% lasers are within a wavelength deviation of ±0.20 nm, corresponding to a tolerance of ±0.032 nm in the period pitch. As a result of employing the equivalent phase shift technique, the single longitudinal mode (SLM) yield is nearly 100%, while the theoretical yield of standard DFB lasers is only around 33.3%.

Broadband antireflection and absorption enhancement by forming nano-patterned Si structures for solar cells

In this letter, we report the antireflection and light absorption enhancement by forming sub-wavelength nano-patterned Si structures via nano-sphere lithography technique. It is found that the surface reflection can be significantly suppressed in a wide spectral range (400-1000 nm) and the weighted mean reflection is less than 5%. Meanwhile, the broad band optical absorption enhancement is achieved consequently. Heterojunction solar cells are prepared by depositing ultrathin amorphous Si film on the nano-patterned Si structures, the short circuit current density increases to 37.2 mA/cm(2)and the power conversion efficiency is obviously improved compared to the reference cell on flat Si substrate.

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.

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.

Experimental demonstration of the corrugation pitch modulated DFB semiconductor laser based on the reconstruction-equivalent-chirp technology

A corrugation-pitch-modulated (CPM) distributed feedback (DFB) semiconductor laser based on reconstruction-equivalent-chirp (REC) technology is first proposed and experimentally demonstrated. The laser operates in good stable single longitudinal mode even the injection current very high.

Monolithically integrated 30-wavelength DFB laser array

To our knowledge, this is the first report of a monolithically integrated distributed feedback (DFB) semiconductor laser array based on reconstruction-equivalent-chirp (REC) technology. A laser bar with 30 different lasers is obtained, lasing at 30 different wavelengths under single longitudinal mode. The typical threshold is about 40mA to 60mA. The typical slope efficiency is about 0.07 mW/mA to .13 mW/mA. Tested under the injection current of 100mA, the side mode suppression ratios (SMSR) range from 24.9dB to 46.8 dB, with an average of 37.2dB. The proposed method is presented in hoping to make a positive contribution to large-scale photonics integrated circuits (PIC) research for the next-generation fiber-optic networks.

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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Based on the equivalent phase shift (EPS) technology, the optical code-division multiple access (OCDMA) en/decoders employing multiple pi-EPSs have been studied both numerically and experimentally, which demonstrate good en/decoding performances. It is also shown that the insertion of multiple pi-EPSs offers a new degree of freedom for OCDMA security, in which the multiple pi -EPSs decoder is completely unmatched with single pi-EPSs encoder even if they have the same code sequence.

Phase Shift Semiconductor Laser for Use in Laser Arrays

A special sampled Bragg grating (SBG) configuration, which consists of two sections with same length and different effective refractive index, is proposed. Because an equivalent λ/4 phase shift based on reconstruction equivalent chirp (REC) technology is introduced, the asymmetric structure can effectively suppress the lasing in its 0th channel, and then its single longitudinal mode (SLM) property is improved. This proposed method can also be used to fabricate high performance multiwavelength laser array (MLA) with high yield.