Guan Bao-Lu

Tunable Vertical-Cavity Surface-Emitting Lasers Integrated with Two Wafers

A novel two-wafer concept for micro-electro-mechanically tunable vertical cavity surface emitting lasers (VCSELs) is presented. The VCSEL is composed by two wafers: one micro-electromechanical-system membrane wafer with four arms to adjust the cavity length through electrostatic actuation and a “half-VCSEL wafer consisting of a fixed bottom mirror and an amplifying active region. The measurement results of the electricity pumped tunable VCSEL with more than 9 mW output power at room temperature over the tuning range prove the feasibility of the proposition.

A Flip-Chip AlGaInP LED with GaN/Sapphire Transparent Substrate Fabricated by Direct Wafer Bonding

A red-light AlGaInP light emitting diode (LED) is fabricated by using direct wafer bonding technology. Taking N-GaN wafer as the transparent substrate, the red-light LED is flip-chiped onto a structured silicon submount. Electronic luminance (EL) test reveals that the luminance flux is 130% higher than that of the conventional LED made from the same LED wafer. Current–voltage (I–V) measurement indicates that the bonding processes do not impact the electrical property of AlGaInP LED in the small voltage region (V 1.5 V), the I–V characteristic exhibits space-charge-limited currents characteristic due to the p-GaAs/n-GaN bonding interface.

Power dissipation in oxide-confined 980-nm vertical-cavity surface-emitting lasers

We presented 980-nm oxide-confined vertical-cavity surface-emitting lasers (VCSELs) with a 16-μm oxide aperture. Optical power, voltage, and emission wavelength are measured in an ambient temperature range of 5 °C–80 °C. Measurements combined with an empirical model are used to analyse the power dissipation in the device and the physical mechanism contributing to the thermal rollover phenomenon in VCSEL. It is found that the carrier leakage induced self-heating in the active region and the Joule heating caused by the series resistance are the main sources of power dissipation. In addition, carrier leakage induced self-heating increases as the injection current increases, resulting in a rapid decrease of the internal quantum efficiency, which is a dominant contribution to the thermal rollover of the VCSEL at a larger current. Our study provides useful guidelines to design a 980-nm oxide-confined VCSEL for thermal performance enhancement.

Micromechanical tunable vertical-cavity surface-emitting lasers

We report the study on a short wavelength-tunable vertical-cavity surface-emitting laser utilizing a monolithically integrated bridge tuning microelectromechanical system. A deformable-bridge top mirror suspended above an active region is utilized. Applied bridge-substrate bias produces an electrostatic force which reduces the spacing of air-gap and tunes the resonant wavelength toward a shorter wavelength (blue-shift). Good laser characteristics are obtained: such as continuous tuning ranges over 11 nm near 940 nm for 0–9 V tuning bias, the peak output power near 1 mW and the full-width-half-maximum limited to approximately 3.2–6.8 nm. A detailed simulation of the micromechanical and optical characteristics of these devices is performed, and the ratio of bridge displacement to wavelength shift has been found to be 3:1.

Low-Threshold and High-Power Oxide-Confined 850 nm AlInGaAs Strained Quantum-Well Vertical-Cavity Surface-Emitting Lasers Based on Intra-Cavity Contacted Structure

The low-threshold and high-power oxide-confined 850 nm AlInGaAs strained quantum-well (QW) vertical-cavity surface-emitting lasers (VCSELs) based on the intra-cavity contacted structure are fabricated. The threshold current of 0.1 mA for a 10-μm oxide-aperture device is obtained with the threshold current density of 0.127 kA/cm2. For a 22-μm oxide-aperture device, the peak optical output power reaches to 14.6 mW at the current injection of 25 mA under the room temperature and pulsed operation with a threshold current of 2 mA, which corresponds to the threshold current density of 0.526 kA/cm2. The lasing wavelength is 855.4 nm. The full wave at half maximum is 2.2 nm. The analysis of the characteristics and the fabrication of VCSELs are also described.