Technical Insight
Semiconductor laser developments (Asia News)
Union Optronics (formerly Sirus Technology), Taiwan s largest manufacturer of red lasers, is planning to increase its output of 1310 nm lasers for the fiber-optic market from 10 000 to 200 000 units per month. The company, which has in-house epiwafer production facilities, was founded to produce 650 nm lasers for DVD players, and is now also developing VCSELs and PIN diodes. A new laser diode from Sanyo has enabled the company to manufacture DVD drives with a 4 write speed, the fastest in the industry. In the device, laser light is confined within the active layer by controlling the refractive index of the cladding layers. This not only improves power emission by reducing loss from the active layer, but also makes the emitted beam shape less elliptical, effectively boosting output power by 20%. The output power of the laser is effectively 100 mW for a drive current of 150 mA. Reducing optical absorption at the facets has also increased the emitted power. This helps to lower the drive current required for a given output power, and improves the device lifetime. Hitachi has developed a red laser emitting at 635 nm with a near circular beam. Most laser diodes have beams with aspect ratios around 3.5. Hitachi s new MARU Beam lasers have an aspect ratio of only 1.2, a figure claimed to be the best in the industry. Both products op-erate at 2.4 V and 25 mA with a 5 mW output power. Future plans are for higher output power versions and a reduction of the aspect ratio to 1.0. Rohm has begun sampling an IR laser designed for CD-RW applications at 16 speed and higher. At 150 mW, the company is claiming the industry s highest output power for this class of device. The compact device comes in a 5.6 mm diameter package, operates at 120 mA and has a wavelength range of 780788 nm. The device is fabricated using selective area epitaxy to give a reduction in optical power loss through absorption in the waveguides. Rohm guarantees 5000 hours of continuous operation thanks to the low optical density of the active region, which reduces catastrophic optical damage.
