Visible VCSEL Research Articles

Speckle Contrast Reduction with a Visible VCSEL Projector

Speckle Contrast Reduction with a Visible VCSEL Projector

Highly efficient active optical interconnect incorporating a partially chlorinated ribbon POF in conjunction with a visible VCSEL.

A low-loss 4-ch active optical interconnect (AOI) enabling passive alignment was proposed and built resorting to a transmitter (Tx) incorporating a red 680-nm VCSEL, which is linked to a receiver (Rx) module via a partially chlorinated ribbon POF. The POF was observed to exhibit an extremely low loss of ~0.24 dB/m at λ = 680 nm, in comparison to ~1.29 dB/m at λ = 850 nm, and a large numerical aperture of ~0.42. Both the Tx and Rx, which taps into a beam router based on collimated beam optics involving a pair of spherical lenses, were meant to be substantially alignment tolerant and compact. The achieved tolerance for the constructed modules was beyond 40 μm in terms of the positioning of VCSEL and photodetector. The proposed AOI was completed by linking the Tx with the Rx via a 3-m long ribbon POF, incurring a transmission loss of as small as 3.2 dB. The AOI was practically assessed in terms of a high-speed data transmission over a wide range of temperatures and then exploited to convey full HD video signals.

In-situ determination of interface roughness in MOVPE-grown visible VCSELs by reflectance spectroscopy

This paper reports on an in-situ optical reflectance study of the development of the interface roughness of AlGaAs/AlAs distributed Bragg reflectors during the metalorganic vapour phase epitaxy growth of visible vertical-cavity surface-emitting laser structures. We show that the surface roughness can be extracted from time-resolved UV reflectance measurements. The roughness of the surface during growth for both the AlGaAs and AlAs layers can be determined individually. The values estimated from the in-situ optical data correlate well with the roughness measured ex-situ using atomic force microscopy. The in-situ reflectance measurement is thus shown to be a convenient non-invasive and non-destructive technique for determining surface and interface roughness even for complex device structures.

80°C continuous wave operation of AlGaInP based visible VCSEL

Singlemode operation of an oxide confined vertical cavity surface emitting laser operating continuous wave around 670 nm up to a heatsink temperature of 80°C is presented. Heatsinking of this device was improved by thinning the GaAs substrate and bonding to a TO-46 header with indium.

Progress in the design and development of AlGaInP visible VCSELs

The design of visible vertical-cavity surface-emitting lasers (VVCSELs) is improved by using numerical simulations based on the drift-diffusion model which take into account such specific features of the VVCSELs as multiple interfaces and indirect bandgaps in the distributed Bragg reflectors (DBRs). The simulation procedures have been tested and refined by comparison with experimental measurements on edge-emitting lasers. These results have been used to analyse a range of design alterations for VVCSELs. VVCSEL structures based on the new designs have been fabricated and show improved characteristics over previous designs, in good agreement with the predicted values.

Room temperature continuous wave visible vertical cavity surface emitting laser

Visible VCSEL laser operated at room temperature continuous wave has been achieved by H+ implants using tungsten wires as an implantation mask. The laser wavelength is 650 nm, and the maximum output without heat-sink exceeds 85 μW at CW operation. We also calculated the thermal resistance of the device.

Efficient room-temperature continuous-wave AlGaInP/AlGaAs visible (670 nm) vertical-cavity surface-emitting laser diodes

Significant improvement in the performance of AlGaInP/AlGaAs visible vertical-cavity surface-emitting laser diodes has been achieved in gain-guided planar-geometry devices utilizing proton implants to define the current injection path. Threshold currents as low as 1.25 mA were measured on 10 /spl mu/m-diameter devices, with maximum power output of 0.33 mW from larger devices. Continuous-wave (cw) lasing was achieved at temperatures as high as 45/spl deg/C. The improved diode performance is attributed to better lateral heat-sinking and reduced parasitic heat generation afforded by the planar device structure, relative to previously-reported air-post structures. This work represents the first realization of efficient room-temperature operation of AlGaInP-based visible VCSEL diodes. >

MOVPE growth of InAlGaP-based visible vertical-cavity surface-emitting lasers

Materials growth issues for visible vertical-cavity surface-emitting lasers have been addressed in detail. For high optical efficiency in the laser cavity, the optical properties of In 0.48(Al y Ga 1- y ) 0.52P quarternary alloys lattice-matched to GaAs were optimized as a function of MOVPE growth parameters including substrate temperature and misorientation. The narrowest photoluminescent linewidths yet reported for all of the direct bandgap In(Al y Ga 1- y )P alloys (0⩽ y⩽0.5) were observed, including 4.2 meV for InGaP. The growth and optical properties of strained quantum well structures were then investigated for use in the laser active region. Structures with a broad range of well and barrier compositions and thicknesses were prepared, and characterized using low-temperature photoluminescence. Based upon this work, high-optical quality strained and unstrained multiple-quantum-well heterostructures were grown for use in the 640–670 nm wavelength range. Epitaxial multilayer dielectric mirror stacks reflecting at visible (620–700 nm) wavelengths were fabricated from the Al 0.5Ga 0.5As/AlAs and InGaP/InAlP systems, and for both types of mirrors excellent reflectivity characteristics were observed. Visible VCSEL structures were grown for photopumping experiments, and the structures exhibited low threshold powers. Wavelength of operation of these structures was in the range 632–661nm.