Laser diode, optical disk device and optical pickup

Abstract

A laser diode capable of performing self-pulsation operation, and capable of sufficiently reducing the coherence of laser light and stably obtaining low-noise laser light is provided. The laser diode includes: a laser chip including at least one laser stripe which extends in a resonator length direction between a first end surface and a second end surface opposed to each other, in which the laser stripe includes a gain region and a saturable absorption region in the resonator length direction, and the width of the laser stripe in the saturable absorption region is larger than the width of the laser stripe in the gain region.

What is claimed is: 
     
         1 . A laser diode comprising:
 a laser chip including at least one laser stripe which extends in a resonator length direction between a first end surface and a second end surface opposed to each other,   wherein,
 the laser stripe includes a gain region and a saturable absorption region in the resonator length direction, 
 the width of the laser stripe in the saturable absorption region is larger than the width of the laser stripe in the gain region, 
 the length of the saturable absorption region is smaller than the length of the gain region, and 
 the saturable absorption regions are arranged on a side close to the first end surface and a side close to the second end surface, and the gain region is arranged between the saturable absorption regions, 
   
     
     
         2 . A laser diode comprising:
 a laser chip including at least one laser stripe which extends in a resonator length direction between a first end surface and a second end surface opposed to each other,   wherein,
 the laser stripe includes a gain region and a saturable absorption region in the resonator length direction, 
 the width of the laser stripe in the saturable absorption region is larger than the width of the laser stripe in the gain region, 
 the length of the saturable absorption region is smaller than the length of the gain region.the gain regions are arranged on a side close to the first end surface and a side close to the second end surface, and 
 the saturable absorption region is arranged between the gain regions. 
   
     
     
         3 . A laser diode comprising:
 a laser chip including at least one laser stripe which extends in a resonator length direction between a first end surface and a second end surface opposed to each other,   wherein,
 the laser stripe includes a gain region and a saturable absorption region in the resonator length direction, 
 the width of the laser stripe in the saturable absorption region is larger than the width of the laser stripe in the gain region, and 
 the laser stripe has a ridge shape, and the lateral refractive index step of the laser stripe in the gain region is different from that in the saturable absorption region. 
   
     
     
         4 . A laser diode comprising:
 a laser chip including at least one laser stripe with a ridge shape which extends in a resonator length direction between a first end surface and a second end surface opposed to each other,   wherein,
 the laser stripe includes a gain region and a saturable absorption region in the resonator length direction, and 
 a lateral refractive index step in the gain region is larger than a lateral refraction index step in the saturable absorption region. 
   
     
     
         5 . An optical disk device comprising:
 a laser diode as a light source,   wherein,
 the laser diode includes at least one laser stripe with a ridge shape which extends in a resonator length direction between a first end surface and a second end surface opposed to each other, 
 the laser stripe includes a gain region and a saturable absorption region in the resonator length direction, and 
 a lateral refractive index step in the gain region is larger than a lateral refraction index step in the saturable absorption region. 
   
     
     
         6 . An optical pick-up comprising:
 a laser diode as a light source,   wherein,
 the laser diode includes at least one laser stripe with a ridge shape which extends in a resonator length direction between a first end surface and a second end surface opposed to each other, 
 the laser stripe includes a gain region and a saturable absorption region in the resonator length direction, and 
 a lateral refractive index step in the gain region is larger than a lateral refraction index step in the saturable absorption region.