Zhenfu Wang

High power and good beam quality of two-dimensional VCSEL array with integrated GaAs microlens array.

High power and good beam quality of two-dimensional bottom-emitting vertical-cavity surface-emitting laser array with GaAs microlens on the substrate is achieved. Uniform and matched convex microlens is directly fabricated by one-step diffusion-limited wet-etching techniques on the emitting windows. The maximum output power is above 1 W at continuous-wave operation at room temperature, and the far-field beam divergence is below 6.6° at a current of 4 A. These properties between microlens-integrated and conventional device at different operating current are demonstrated.

High-power vertical-cavity surface-emitting laser with an optimized p-contact diameter

A 980 nm bottom-emitting vertical-cavity surface-emitting laser (VCSEL) with a p-contact diameter is reported to achieve high power and good beam quality. A numerical simulation is conducted on the current spreading in a VCSEL with oxidation between the active region and the p-type distributed Bragg reflector. It is found that, for a particular oxide aperture diameter, somewhat homogeneous current distribution can be achieved for a VCSEL with an optimized p-contact diameter. The far-field divergence angle from a 600 microm diameter VCSEL is suppressed from 30 degrees to 15 degrees, and no strong sidelobe is observed in the far-field pattern by using the optimized p-contact diameter. There is a slight rise in threshold and optical output power that is due to the p-contact optimization. By improving the device packaging method, the maximum optical output power of the device is 2.01 W.

Design and comparison of GaAs, GaAsP and InGaAlAs quantum-well active regions for 808-nm VCSELs

Vertical-cavity surface-emitting lasers emitting at 808 nm with unstrained GaAs/Al0.3Ga0.7As, tensilely strained GaAs(x)P(1-x)/Al0.3Ga0.7As and compressively strained In(1-x-y)Ga(x)Al(y)As/Al0.3Ga0.7As quantum-well active regions have been investigated. A comprehensive model is presented to determine the composition and width of these quantum wells. The numerical simulation shows that the gain peak wavelength is near 800 nm at room temperature for GaAs well with width of 4 nm, GaAs0.87P0.13 well with width of 13 nm and In0.14Ga0.74Al0.12As well with width of 6 nm. Furthermore, the output characteristics of the three designed quantum-well VCSELs are studied and compared. The results indicate that In0.14Ga0.74Al0.12As is the most appropriate candidate for the quantum well of 808-nm VCSELs.

High-Power Large-Aperture Bottom-Emitting 980-nm VCSELs With Integrated GaAs Microlens

Microlens-integrated bottom-emitting 980-nm vertical-cavity surface-emitting lasers (VCSELs) with an emitting window aperture of 400 mum have been fabricated. A novel material structure with nine InGaAs-GaAsP quantum wells and slightly decreased reflectivity of n-type distributed Bragg reflectors (n-DBRs) are employed to increase the output power. A convex microlens is fabricated by a one-step diffusion-limited wet-etching technique on the GaAs substrate. The diameter of the active layer is about 200 mum after lateral oxidation, and the nominal diameter of the microlens is 400 mum. The maximum output power is 200 mW at continuous-wave operation at room temperature. The far-field divergence angles thetas|| and thetasperp of the single device at a current of 4A are 8.7deg and 8.4deg, respectively. The optical beam performance between the microlens-integrated VCSEL and ordinary VCSEL is compared.

Design and characterization of a nonuniform linear vertical-cavity surface-emitting laser array with a Gaussian far-field distribution

A 980 nm bottom-emitting vertical-cavity surface-emitting laser array with a nonuniform linear arrangement is reported to realize emission with a Gaussian far-field distribution. This array is composed of five symmetrically arranged elements of 200 microm, 150 microm, and 100 microm diameter, with center spacing of 300 microm and 250 microm, respectively. An output power of 880 mW with a high power density of 1 kW/cm2 is obtained. The divergence angle is below 20 degrees in the range of operating current from 0 A to 6 A. The theoretical simulation of the near-field and the far-field distribution is in good agreement with the experimental result. The comparison between this nonuniform linear array, the single device, and the conventional two-dimensional array is carried out to demonstrate the good performance of the linear array.

Central hole effect on Whispering-Gallery-Mode of Triangular Lattice Photonic Crystal Microcavity

Whispering-Gallery-Mode (WGM) photonic crystal microcavity is a kind of photonic crystal application and can potentially be used for miniaturized photonic devices, such as thresholdless lasers. In this paper we study the WGM of photonic crystal microcavities focusing on the so called H2 cavities which are formed by removing seven air holes. The WGM in these large-size cavities has some advantages compared with single defect WGM in the view of real device applications. We further add a central air hole in the cavity region to analyze the effect on WGM in the microcavity by finite difference time domain (FDTD) and plane wave expansion (PWE). It is found that the tolerance of WGM is large enough for the fabrication of electrical injection structure.

A novel bottom-emitting VCSEL's one-dimension array

A novel 980nm bottom-emitting VCSELs array with high power density and good beam property of Gaussian far-field distribution is reported. This array is composed of 5 symmetrically-arranged elements of 200&μm,150μm and 100μm-diameterμwith the center spacings of 300μm and 250μm respectively. The maximum power is 880mW at a current of 4A, corresponding to 1KW/cm2 average optical power density. The differential resistance is Ω with a threshold of 0.56A. The novel array is compared with a 300μm-aperture-size single device and a 4*4 2-D array with 50μm element aperture size and 250μm centre spacing. The three devices have the same lasing area. The conclusion is that the novel array is better in the property of output power, threshold current, lasing spectra, far-field distribution etc.