Tunable semiconductor diode laser DISTRIBUTED WITH REFLECTION AND MANUFACTURING METHOD OF SUCH SEMICONDUCTOR LASER DIODE.

摘要

A tunable semiconductor diode laser with distributed reflection (DBR semiconductor lasers) having a wide wavelength range is a suitable transmitter or local oscillator in a receiver in heterodyne and coherent optical glass fibre communication systems. Such a diode comprises beside the Bragg section (c) in which the Bragg reflection takes place an active section (4) in which the radiation-emitting active region (13) is present. When such a semiconductor diode laser is further provided with a so-called phase section (B), tuning is possible over a large wavelength range within one oscillation mode. It has been found, however, that so-called forbidden zones where no oscillation within the given mode is possible are formed in the wavelength range over which the laser is tunable. According to the invention, a laser which is continuously tunable over the whole wavelength range is obtained by providing means (21) with which the intensity of radiation which is reflected at the junction between the active section (A) and the phase section (B) is made low with respect to the intensity of the radiation which returns from the phase section (B) to the active section (A). These means comprise an extra radiation-conductive layer (21) in the phase section (B) which adjoins and smoothly merges into the active region (13) situated in the active section (A). When the active section (A) is present centrally in the Bragg section (C) and the phase section (B) the means may also comprise a high-reflecting coating (56) which is present on a free side of the phase section (B). In the latter case the means may also comprise the said extra radiation-conductive layer. The extra radiation-conductive layer (21) and the active region of the first radiation-conductive layer (11) are preferably separated by a passive layer (12) having such a thickness that the said layers (11, 13) are situated within each others amplification profile.