Coherent light generators – Particular beam control device – Tuning
Patent
1997-08-28
1999-03-30
Bovernick, Rodney
Coherent light generators
Particular beam control device
Tuning
372 26, 372 38, 372 50, H01S 310, H01S 300, H01S 319
Patent
active
058898018
ABSTRACT:
A driving method for a tunable semiconductor laser which is remarkably effective for realizing high speed and stable wavelength switching is presented. Generally, when a single longitudinal mode laser oscillation wavelength of a tunable semiconductor laser diode comprising an active region and a wavelength control region is switched from .lambda..sub.1 to .lambda..sub.2, a wavelength control current (.lambda.-Control) supplied to the wavelength control region is switched from I.sub.1 to I.sub.2. In the driving method according to the present invention, an active layer current (Active) supplied to the active region is temporarily decreased below a predetermined value during a predetermined period, in order to temporarily stop the single longitudinal mode laser oscillation of the laser diode. Preferably, the length of the predetermined period is set longer both before and after the moment of the wavelength control current switching than at least the carrier lifetime in the wavelength control region, and the predetermined value of the active layer current is set below threshold currents of all longitudinal modes existing between longitudinal modes corresponding to oscillation wavelengths before and after the wavelength control current switching. According to the driving method, oscillations at undesirable longitudinal modes are prevented, and thus stable high speed wavelength switchings precisely following supplied wavelength control signals are made possible even in a laser such as a tunable DBR laser diode involving longitudinal mode hops.
REFERENCES:
patent: 4719636 (1988-01-01), Yamaguchi et al.
patent: 4823352 (1989-04-01), Sugimoto
patent: 4873691 (1989-10-01), Uomi et al.
patent: 4920542 (1990-04-01), Brosson et al.
patent: 5541945 (1996-07-01), Yamaguchi et al.
Kato Tomoaki
Yamada Yoshiaki
Bovernick Rodney
Leung Quyen Phan
NEC Corporation
Nippon Telegraph and Telephone Corporation
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