Jon Geske

Vertical-cavity surface-emitting laser active regions for enhanced performance with optical pumping

We have developed an improved active region design for optically pumped vertical-cavity surface-emitting lasers. The design makes use of carrier-blocking layers to segment the absorber and promote uniform carrier populations in the quantum wells with pump efficiencies near 75%. A model to calculate the carrier distribution in the active region and a design methodology are presented along with a metric to describe the carrier uniformity in the quantum wells. Experimental verification of the performance improvements shows an over 50% reduction in device thresholds and an increase of 20/spl deg/C in maximum operating temperatures.

Low dark current InGaAs detector arrays for night vision and astronomy

Aerius Photonics has developed large InGaAs arrays (1K x 1K and greater) with low dark currents for use in night vision applications in the SWIR regime. Aerius will present results of experiments to reduce the dark current density of their InGaAs detector arrays. By varying device designs and passivations, Aerius has achieved a dark current density below 1.0 nA/cm2 at 280K on small-pixel, detector arrays. Data is shown for both test structures and focal plane arrays. In addition, data from cryogenically cooled InGaAs arrays will be shown for astronomy applications.

Temperature dependence of the relaxation resonance frequency of long-wavelength vertical-cavity lasers

The temperature dependence of the differential gain in AlInGaAs 1310-nm vertical-cavity lasers is investigated. The variations in differential gain and in relaxation resonance frequency are shown to depend on the room-temperature offset between the gain peak wavelength and the wavelength of the lasing mode. The tradeoff between high modulation bandwidth and good high-temperature performance for vertical-cavity lasers is analyzed. A cavity mode that is red-shifted about 25 nm from the gain peak is shown to minimize the variation in modulation bandwidth with temperature, and simultaneously allow for satisfactory high-temperature operation. Experimental results are presented and compared to calculated results with excellent agreement. Because of the change in gain-mode offset with internal temperature, the measured modulation current efficiency changed from about 2 to 4.8 GHz/mA/sup 1/2/ for an increase in drive current from 2 to 10 mA.

1.3 μm wavelength vertical cavity surface emitting laser fabricated by orientation-mismatched wafer bonding: A prospect for polarization control

We propose and demonstrate a long-wavelength vertical cavity surface emitting laser (VCSEL) which consists of a (311)B InP-based active region and (100) GaAs-based distributed Bragg reflectors (DBRs), with an aim to control the in-plane polarization of output power. Crystal growth on (311)B InP substrates was performed under low-migration conditions to achieve good crystalline quality. The VCSEL was fabricated by wafer bonding, which enables us to combine different materials regardless of their lattice and orientation mismatch without degrading their quality. The VCSEL was polarized with a power extinction ratio of 31 dB.

Long-wavelength two-dimensional WDM vertical cavity surface-emitting laser arrays fabricated by nonplanar wafer bonding

We demonstrate the first long-wavelength two-dimensional wavelength-division-multiplexed vertical cavity surface-emitting laser array. The eight-channel single-mode array covers the C-band from 1532 to 1565 nm. The devices are fabricated using two separate active regions laterally integrated using nonplanar wafer bonding. We achieved single-mode powers up to 0.8 mW, 2-dB output power uniformity across the array, and sidemode suppression ratios in excess of 43 dB. This fabrication technique can be used to maintain the gain-peak and cavity-mode alignment across wide-band arrays and, with the use of nontraditional mirrors, can be extended to the fabrication of arrays covering the entire C-, S-, and L-bands as well as the 1310-nm transmission band.

2.5-Gb/s transmission over 50 km with a 1.3-μm vertical-cavity surface-emitting laser

We demonstrate error-free 50-km transmission at 2.5 Gb/s over standard single-mode fiber using an optically pumped 1.3-/spl mu/m vertical-cavity surface-emitting laser operating at 25/spl deg/C. No optical isolator or amplification was used in the transmission demonstration. System backreflection sensitivity measurements were conducted for various fiber distances and reflection feedback levels. The results indicate a transmission power penalty of 0.1 dB at a bit-error rate of 10/sup -9/ for a reflection feedback level of -25 dB with the reflection originating at 5 m.

Wide-area SWIR arrays and active illuminators

We describe the factors that go into the component choices for a short wavelength (SWIR) imager, which include the SWIR sensor, the lens, and the illuminator. We have shown the factors for reducing dark current, and shown that we can achieve well below 1.5 nA/cm2 for 15 μm devices at 7°C. We have mated our InGaAs detector arrays to 640x512 readout integrated integrated circuits (ROICs) to make focal plane arrays (FPAs). In addition, we have fabricated high definition 1920x1080 FPAs for wide field of view imaging. The resulting FPAs are capable of imaging photon fluxes with wavelengths between 1 and 1.6 microns at low light levels. The dark current associated with these FPAs is extremely low, exhibiting a mean dark current density of 0.26 nA/cm2 at 0°C. FLIR has also developed a high definition, 1920x1080, 15 um pitch SWIR sensor. In addition, FLIR has developed laser arrays that provide flat illumination in scenes that are normally light-starved. The illuminators have 40% wall-plug efficiency and provide low-speckle illumination, provide artifact-free imagery versus conventional laser illuminators.

Dual-wavelength vertical-cavity surface-emitting laser arrays fabricated by nonplanar wafer bonding

A dual-wavelength 1550 nm and 1530 nm VCSEL array is fabricated using two separate and distinct active regions integrated on a common mirror by nonplanar wafer bonding.

Simplified nonplanar wafer bonding for heterogeneous device integration

We demonstrate a new, simplified nonplanar wafer bonding technique for heterogeneous device integration. The improved technique can be used to laterally integrate dissimilar semiconductor device structures on a lattice mismatched substrate. Using the technique two InP based VCSEL active regions have been integrated onto GaAs without compromising the quality of the photoluminescence. Experimental and numerical simulation results are presented.

Uniform optical pumping design for 1.55 /spl mu/m VCSELs

Numerical laser simulation of new active region design which provides more uniform gain using carrier blocking layers between the quantum wells is presented. The laser model includes calculations of optical carrier generation, carrier transport from the absorber layers to the quantum wells, quantum well gain, and optical field. The model is designed to compensate the non-uniform optical pumping of the quantum wells.