Nobuaki Ueki

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.

Complete Polarization Control of 12×8-Bit Matrix-Addressed Oxide-Confined Vertical-Cavity Surface-Emitting Laser Array

The authors have shown complete polarization control of a 12×8-bit matrix-addressed oxide-confined vertical-cavity surface-emitting laser (VCSEL) array, which has an unstrained active region emitting at 780 nm. By using a combination of an elliptical-shaped post structure fabricated on misoriented substrate and upper p-side metal lines elongated in the substrate off-direction, we observed complete polarization pinning in an index-guide type array device. All of the VCSELs in this array lased in a fundamental transverse mode and linearly polarized along the direction.

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

VCSEL-Based Laser Printing System

There is an endless demand for improved image quality and higher speed in printer applications. To meet market requirements, in 2003 we launched DocuColor 1256 GA, the world’s first VCSEL-based electrophotographic printer utilizing a 780 nm single-mode \(8{}\times{}4\) VCSEL array. The printer features 2,400 dots per inch (dpi ) resolution, which is still the highest level in the industry, and a speed of 12.5 pages per minute (ppm ). A two-dimensional VCSEL array makes it much easier to increase the pixel density and printing speed by simultaneously scanning the 32 beams on the photoconductor in the light exposure system . Adopting VCSELs as a light source also contributes to reduced power consumption, because the operating current of VCSELs is extremely small and the wall-plug efficiency is very high. In this chapter, we explain the key technologies of VCSELs in light exposure system of laser printer, as well as their required characteristics to assure high image quality.

Characteristics and Reliability of 10 Gbps/Channel 1 ×10 Vertical-Cavity Surface-Emitting Laser Array of 850 nm Wavelength

A 10 Gbps/channel 1 ×10 vertical-cavity surface-emitting laser (VCSEL) array of 850 nm wavelength was demonstrated for a 100 Gbps (10 Gbps × 10) local area network. The VCSEL array was oxidized using an in situ probing technique. The threshold current of each VCSEL on the array is approximately 0.5 mA with the oxide and metal apertures of 8 and 6 µm, respectively. The temperature characteristic of lasing from -40 to 120 °C was stable and the f-3 dB cutoff frequency exceeded 10 GHz at 6 mA. The data transmission test through the conventional multimode fiber of 300 m length was carried out. We also investigated the reliability of the VCSEL array at an ambient temperature of 120 °C and a dc current of 15 mA. We could achieve a failure rate over a decade below 1% at a temperature and current of 60 °C and 7 mA, respectively.