Visible Vertical Cavity Surface Research Articles

Loss analysis in nitride deep ultraviolet planar cavity

In recent decades, literatures about visible vertical cavity surface emitting lasers (VCSELs) have been reported. However, due to high optical loss in the cavity, lasing from deep ultraviolet (DUV) VCSEL was still rarely achieved. The optical loss in nitride DUV microcavity was analyzed in detail. DUV nitride vertical Fabry–Perot microcavity with active layer of AlGaN-based quantum dots and double-side HfO2 / SiO2 distributed bragger reflectors was fabricated. Optical losses with of the order of 103 cm − 1 were deduced from the Q value of the cavity modes. The main origination of optical loss in DUV cavity was calculated and ascribed to the interface scattering. The interface roughness appearing after laser lift-off process and overlap between rough interface and standing optical wave were two key parameters that contributed to interface scattering loss. We believe that our results will provide useful information for improving DUV VCSEL devices.

Bidirectional optical transcutaneous telemetric link for brain machine interface

A wavelength division multiplexing-based bidirectional optical transcutaneous telemetric data link for brain machine interfaces is reported. By converting the digitised electronic signals to a stream of infrared and visible optical pulses, the optical telemetry wirelessly transmits data between the implanted neural recorder/stimulator and the external control devices. A red visible vertical cavity surface emitting laser (VCSEL) with a peak wavelength of 680 nm is used in the downlink to transmit data from the external base unit to the implant. A near infrared VCSEL with a peak wavelength of 850 nm is utilised in the uplink for data transmission from the implants to the external device. An optical filter is applied to minimise the interference between the two channels. In-vitro experiments show that the uplink is capable of transmitting data at 100 Mbps through 2 mm of porcine skin while the downlink is simultaneously working at a rate of 1 Mbps. The power consumption of the implant part of the telemetry, including the transmitter for the uplink and the receiver for the downlink are 3.2 mW and 290 μW, corresponding to a transmission power efficiencies of 32 and 290 pJ/bit, respectively, which are among the best reported and unseen for bidirectional high-speed transcutaneous communication.

MOVPE process development for 650 nm VCSELS using optical in-situ techniques

In this paper we report on the optimization and control of key layer properties of visible vertical cavity surface emitting laser (VCSEL) for emission at wavelengths around 650 nm by means of an optical real-time sensor allowing for both spectroscopic reflectance and reflectance anisotropy measurements. In contrast to conventional ex-situ characterization the in-situ sensor yields information on properties like thickness, composition and doping for all buried layers, especially the lower distributed Bragg reflector which has a strong influence on the final device performance. Using in-situ sensor-based optimization of the growth process 650 nm VCSEL devices with a record-high continuous-wave output power of 3 mw at room temperature have been fabricated.

Assessing the Performance of Visible (665 nm) Vertical Cavity Surface Emitting Lasers Using High Pressure and Low Temperature Techniques

The effects of carrier leakage and gain-cavity alignment on the temperature dependence of the threshold current (I th ) in visible vertical cavity surface emitting lasers (VCSELs) are investigated. In order to assess the two effects and the degree to which they couple we have performed pressure and temperature experiments on VCSELs and their equivalent edge emitting lasers (EEL). We have established that the peak of the gain moves with pressure at a rate of 72 meV GPa -1 more than three times the rate of 22 meV GPa -1 for the cavity mode. However, we show that over the temperature operating range carrier leakage into the indirect X-minima is the major contributor to an increased I th , nevertheless optimised gain-cavity alignment can lead to more stable operation.

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.

Polarisation characteristics of InGaAlP/AlGaAs visiblevertical cavity surface emitting lasers

The first observation of polarisation selectivity in In/sub 0.48/Ga/sub 1-x/Al/sub x/P based visible vertical cavity surface emitting lasers grown on 10/spl deg/ off axis

Visible vertical cavity surface emitting lasers at λ < 650 nm

The room temperature operation of visible vertical cavity surface emitting lasers at 642 nm is reported. A pulsed threshold current of 45 mA for a 26 μm diameter mesa device (corresponding to 8.5 kA cm −2) was achieved at an operating voltage of 3.5 V. Photoluminescence at 10 K showed that an In 0.48Al 0.3Ga 0.22P direct barrier provides better electron confinement than an In 0.48Al 0.52P indirect barrier with unstrained In 0.48Ga 0.52P quantum wells.

AlGaInP visible vertical cavity surface emitting lasers operating with gain contributions from the n=2 quantum well transition

We report the characteristics of visible vertical cavity surface emitting laser diodes. Wafers are grown such that the Fabry–Perot resonance wavelength changes with position from 690 to 620 nm, overlapping to varying degrees with the n=1 and n=2 quantum well gain peaks at ∼670 and 650 nm. Gain guided devices are tested across the entire wafer, and pulsed room temperature lasing is observed from 634.6 to 663.2 nm. Our results suggest that gain contributions from the second quantized state are required to overcome high cavity losses in order to achieve lasing.

Room temperature continuous wave operation of red vertical cavity surface emitting laser diodes

The first room temperature (23°C) continuous wave visible vertical cavity surface emitting laser diodes are reported. Annular contact devices with a 5 μm optical aperture in a 15 μm diameter mesa emit at 670.4 nm with a threshold current of 5 mA at 2.4V. Devices with 20–60 μm diameter mesas operate continuous wave below −13°C.