Xie Yiyang

A Single-Fundamental-Mode Photonic Crystal Vertical Cavity Surface Emitting Laser

Single-fundamental-mode photonic crystal (PhC) vertical cavity surface emitting lasers (VCSEL) are produced and their single-fundamental-mode performances are investigated and demonstrated. A two-dimensional PhC with single-point-defect structure is fabricated using UV photolithography and inductive coupled plasma reactive ion etching on the surface of the VCSELs top distributed Bragg-reflector. The PhC VCSEL maintains single-fundamental-mode operating with output power 1.7 mW and threshold current 2.5 mA. The full width half maximum of the lasing spectrum is less than 0.1 nm, the far field divergence angle is less than 10 degrees and the side mode suppression ratio is over 35 dB. The device characteristics are analyzed based on the effective index model of the photonic crystal fiber. The experimental results agree well with the theoretical expectation.

Thermal Analysis of Implant-Defined Vertical Cavity Surface Emitting Laser Array

A three-dimensional electrical-thermal coupling model based on the finite element method is applied to study thermal properties of implant-defined vertical cavity surface emitting laser (VCSEL) arrays. Several parameters including inter-element spacing, scales, injected current density and substrate temperature are considered. The actual temperatures obtained through experiment are in excellent agreement with the calculated results, which proves the accuracy of the model. Due to the serious thermal problem, it is essential to design arrays of low self-heating. The analysis can provide a foundation for designing VCSEL arrays in the future.

Polarization Stable Vertical Cavity Surface Emitting Laser Array Based on Proton Implantation

Polarization stable characteristic of vertical cavity surface emitting laser array with rectangular element structure based on proton implantation is achieved. Arrays with different aperture sizes and different array scales are investigated. The maximum orthogonal polarization suppression ratio of a 6 × 6 array with 6 μm; × 4 μm elements is as high as 16.1 dB at 51 mA. The x-polarization dominates y-polarization in the operation current range from the threshold to the saturated current. The full widths at half maximum in far-field profiles for x-polarization and y-polarization are 8.8° and 10.7°, respectively. These results suggest that stable polarization is available in the implant-defined VCSEL array.

Vertical cavity surface emitting laser transverse mode and polarization control by elliptical hole photonic crystal

The polarization of traditional photonic crystal (PC) vertical cavity surface emitting laser (VCSEL) is uncontrollable, resulting in the bit error increasing easily. Elliptical hole photonic crystal can control the transverse mode and polarization of VCSEL efficiently. We analyze the far field divergence angle, and birefringence of elliptical hole PC VCSEL. When the ratio of minor axis to major axis b/a = 0.7, the PC VCSEL can obtain single mode and polarization. According to the simulation results, we fabricate the device successfully. The output power is 1.7 mW, the far field divergence angle is less than 10°, and the side mode suppression ratio is over 30 dB. The output power in the Y direction is 20 times that in the X direction.

Single-mode low threshold current multi-hole vertical-cavity surface-emitting lasers

A multi-hole vertical-cavity surface-emitting laser (VCSEL) operating in stable single mode with a low threshold current was produced by introducing multi-leaf scallop holes on the top distributed Bragg-reflector of an oxidation-confined 850 nm VCSEL. The single-mode output power of 2.6 mW, threshold current of 0.6 mA, full width of half maximum lasing spectrum of less than 0.1 nm, side mode suppression ratio of 28.4 dB, and far-field divergence angle of about 10° are obtained. The effects of different hole depths on the optical characteristics are simulated and analysed, including far-field divergence, spectrum and lateral cavity mode. The single-mode performance of this multi-hole device is attributed to the large radiation loss from the inter-hole spacing and the scattering loss at the bottom of the holes, particularly for higher order modes.