Semiconductor laser device

Method for reducing linewidth and frequency noise in a laser device (100;

• 200;
• 300;
• 400;
• 500) comprising a laser (110;
• 210;
• 310;
• 410;
• 510) in turn comprising at least one Distributed Bragg Reflector (DBR) section (111;
• 211;
• 311;
• 411;
• 511), at least one phase section (112;
• 212;
• 312;
• 412;
• 512) and at least one gain section (113;
• 214;
• 313;
• 413;
• 513),
• which laser device further comprises a laser control means (150;
• 250;
• 350;
• 450;
• 550), arranged to feed respective tuning currents to the said at least one DBR section, to the said at least one phase section and to at least one gain section in order to tune the laser,
• wherein the laser device is provided with a feedback control means (140;
• 240;
• 340;
• 440;
• 540) and a frequency noise discriminator (130,131;
• 230,231;
• 330,331;
• 430,431;
• 530,531) in communication with said feedback control means,
• wherein the frequency noise discriminator is caused to detect a frequency fluctuation in a light beam (116;
• 216;
• 316;
• 416;
• 516) output from the laser and to communicate a signal representing the frequency fluctuation to the feedback control means,
• wherein the feedback control means is caused to feed a respective variable electric feedback signal to at least one of said at least one DBR section and said at least one phase section of the laser, so that the output laser frequency is altered in response to a variation in the feedback signal or the combination of respective feedback signals, whereby the feedback signal or combination of respective feedback signals is varied as a function of the detected frequency fluctuation so as to counteract the detected frequency fluctuation.