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New 4-beam Lasers and Laser Drivers for High-performance Laser Printers and Copiers

New Semiconductor Products for Laser Printers and Copiers

	4-Beam Common-Anode Laser Diode SLD268MS
	4-Beam Common-Anode Laser Driver CXA3814R

Copiers and laser printers use electrophotographic technology that prints using the following five processes: (1) Charging, (2) Exposing, (3) Developing, (4) Transferring and (5) Fixing. (See figure 1.) A semiconductor laser is indispensable to the (2) Exposing process. In the exposing process, a polygon mirror reflects a laser beam to irradiate and scan a photoreceptor. (See figure 2.)
Print speed and resolution are important performance indicators for copiers and laser printers. Print speed can be increased mechanically by raising polygon mirror rotation or using multi-faceted mirrors, or optically by using a multiple beam system that simultaneously scan multiple laser beams. Sony has already conducted more than 10 years of research in multibeam lasers for the latter system. Sony holds a 55% or larger share^*1 of the multibeam laser printer market and an 87% or larger share^*1 of high-performance multibeam systems involving four or more beams, which show the respect our products enjoy.
Printers with four or more beams used to be high-end systems. However, the demand for higher speeds and higher resolutions is expected to raise the share of such printers. To meet this demand, Sony has newly developed the SLD268MS, a compact, 4-beam common-anode laser diode and the CXA3814R, 4-beam common-anode laser driver, which maximizes the potential of the laser. Thanks to technology developed by Sony, the design of a drive circuit tailored to laser device characteristics and the combination of the the laser and driver in a product made it possible to simplify a board design that fully utilizes its characteristics.

*1: As of January, 2012 (based on Sony's research)

4-Beam Common-Anode Laser Diode [SLD268MS]

Sony's unique SDH structure has allowed us to fit a low threshold current laser in a compact 5.6 mm diameter package to produce a new generation 4-beam laser with even more advanced high-performance and cost-effectiveness

- 30 μm pitch 4-beam laser
- Threshold current value: 4 mA
- Rated optical power output/maximum optical power output: 10 mW/15 mW
- 5.6 mm diameter 6-pin package

Sony provides a lineup of light sources for copiers and laser printers that ranges from single-beam to 8-beam lasers. As the number of beams increases, the characteristics drop due to greater heat generation. To better cool the laser, it used to be placed in a large package, but this became a cost barrier that made it difficult to introduce lasers with four or more beams to a wider market.
Improvements in Sony's SDH structure lowered the threshold current resulting in less generated heat and made it possible to integrate the laser in a more compact package. (See photograph 1.) This achievement is expected to increase the market appeal of 4-beam laser products.

Crystal Growth Process
In the SDH structure, a crystal growth is formed on a specially processed GaAs substrate in a single crystal growth process that produces the laser structure. The current-blocking layer blocks current more efficiently than other structures. The formation of the block layer is a vital characteristic of this structure where the selection of a dopant is essential in improving its current control characteristics. The SLD268MS uses a new type of dopant that produces a more stable current block layer structure. (See figure 3.)

Electrode Formation Process
In 4-beam lasers made so far, the solder electrodes independently controlled each beam. However, the SLD268MS has an air bridge, a multilayer interconnection technology, to obtain greater stability in the narrow pitch process.

Wire Formation Process
Five types of wire bonds are required in a 4-beam laser if PD wires are included. Compact φ5.6 mm packages require much finer wire than that used in existing φ9 mm packages. The numerous environmental tests that the SLD268MS has been put through have confirmed the strength of the high-quality wire bonding. (See photograph 2.)

Development team members
(From left, back row) Tetsuya Hirama, Fumitake Oikawa, Eiji Takase,
Kazuki Wakatsuki, Sachio Karino and (front row) Shoji Honda

4-Beam Common-Anode Laser Driver [CXA3814R]

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Vol.68

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