Hiromi Otoma

Single-transverse-mode 3.4-mW emission of oxide-confined 780-nm VCSELs

The authors have fabricated oxide-confined vertical-cavity surface-emitting lasers with metal apertures exhibiting a spatial mode filtering effect. Single-mode continuous-wave output is enhanced up to 3.4 mW by this effect for AlGaAs-based 780-nm vertical-cavity surface-emitting lasers with a 3.5-/spl mu/m-diameter oxide aperture. From numerical calculations, the round-trip loss difference between zeroth- and first-order optical modes as a function of metal aperture size indicates that there is an optimum point; a 4-/spl mu/m metal aperture size is suitable for higher order mode suppression of a 3.5-/spl mu/m oxide aperture device.

VCSEL array-based light exposure system for laser printing

Improving the image quality and speed is an endless demand for printer applications. To meet the market requirements, we have launched the world first laser printer (DocuColor 1256 GA) introducing 780-nm single-mode 8×4 VCSEL arrays in the light exposure system in 2003. The DocuColor 1256 GA features 2400 dots per inch (dpi) resolution which is the highest in the industry and a speed of 50 pages per minute (ppm). A VCSEL array design has an advantage that it can increase the pixel density and also increase the printing speed by simultaneously scanning the 32-beam to the photoconductor in the exposure process. Adopting VCSELs as a light source also contributes to the reduction of the machines power consumption. The VCSELs are industrially manufactured based on the original in-situ monitored oxidation process to control the oxide aperture size. As a result, uniform characteristics with a less than 5% variation in both output power and divergence angle are obtained. Special care is also taken in the assembly process to avoid additional degradation in performance and quality. This technology is currently extended to high-end tandem color machines (2400 dpi, 80 ppm) to grasp on-demand publishing market. This paper will cover the key technologies of the VCSEL based light exposure system as well as its manufacturing process to assure its quality.

Single-Mode Oxide-Confined VCSEL for Printers and Sensors

The 850nm single-mode oxide-confined VCSEL with a metal aperture as a spatial mode filter is reported. The OPTALO (optical probing technique for AlAs lateral oxidation) process was adopted to manufacture a small oxide aperture in VCSEL with high reproducibility. The combination of a metal-aperture and an oxide-aperture brought good performance to 850nm single-mode VCSEL. The fundamental transverse mode oscillation was obtained up to 4.7mW output power. The SMSR is larger than 27dB. No kinks in the L-I curves were observed under -40 to 95degC temperature range. The laser beam is selectively polarized in parallel to the lang0.1-1rang orientation of the GaAs substrate. We also developed the 780nm single-mode VCSEL array (8times4) for laser beam printer application. The polygon scanner system incorporating this 780nm single-mode VCSEL array made it possible to achieve 2400 DPI high dense printing together with 80ppm high speed print

Developments of VCSELs for printers and optical communications at Fuji Xerox

We review the characteristics of vertical-cavity surface-emitting lasers (VCSELs) for use in printers and optical communications. In 2003, we launched the worlds first laser printer with a 780-nm single-mode 8×4 VCSEL array introduced to the light exposure system in order to meet the market demands for improving the image quality and speed for laser printers. The design of the VCSEL array enabled us to increase the pixel density and the printing speed by projecting 32 beams at a time to the photoconductor in the exposure process. High uniformity with less than 5% of variation has been achieved for both the optical output and the divergence angle. Currently, our high-end color printer is capable of producing the resolution of 2400 dpi (dots per inch) at the speed of 137 ppm (pages per minute). In the field of optical interconnections and networks, 850-nm VCSELs are needed as high-speed optical transmitters (≥10Gbps). In order to address communication traffic that will increase further as well as to reduce their power consumption to an even lower level, we assessed the lasing characteristics of 850-nm VCSELs with InGaAs strained quantum-well (QW) active layers by changing the ratio of Indium composition. As a result, we succeeded in reducing the power consumption per bit to 43 fJ/bit at 10-Gbps, which is much lower than that of commercial GaAs QW VCSELs. Also, we studied 850-nm transverse-coupled-cavity VCSELs, which enabled us to achieve a high 3dB modulation bandwidth (>23 GHz) and realize eye-openings at the large-signal modulation rate of 36 Gbps.