GaN semiconductor laser device, and optical disk information system using the laser device
Two or more of striped structures are formed in one chip, and a relaxation oscillation frequency of the first striped structure is greater than a relaxation oscillation frequency of the second striped structure. An RIN value at low output is improved by the first striped structure having a higher relaxation oscillation frequency, and a single transverse mode and reliability at high output are obtained by the second striped structure having a lower relaxation oscillation frequency.
1. A GaN-based semiconductor laser device comprising:
in one laser chip, an insulating substrate, a first striped structure on said insulating substrate and having a first relaxation oscillation frequency fr 1 , and a second striped structure on said insulating substrate and having a second relaxation oscillation frequency fr 2 ,
wherein a length of said first striped structure is less than a length of said second striped structure, and an average of a front-face reflectance and a back-face reflectance of said first striped structure is greater than an average of a front-face reflectance and a back-face reflectance of said second striped structure, such that the first relaxation oscillation frequency fr 1 is greater than the second relaxation oscillation frequency fr 2 , and
wherein a trench is between said first striped structure and said second striped structure, with said insulating substrate being exposed at a bottom of said trench such that a current path between said first striped structure and said second striped structure does not exist.
2. The GaN based semiconductor laser device according to claim 1 , further comprising:
a first p-electrode on said first striped structure;
a second p-electrode on said second striped structure; and
an n-electrode on the same side of said one laser chip as is said p-electrodes.
3. The GaN based semiconductor laser device according to claim 2 , wherein
said n-electrode is common to said first and second striped structures.
4. The GaN based semiconductor laser device according to claim 3 , wherein
said n-electrode is adjacent to said second striped structure.
5. The GaN based semiconductor laser device according to claim 4 , wherein
said first striped structure is for reading, and
said second striped structure is for writing.
6. The GaN-based semiconductor laser device according to claim 5 , wherein
said first relaxation oscillation frequency fr 1 and said second relaxation oscillation frequency fr 2 satisfy a relational expression of (fr 1 −fr 2 )/fr 2 >0.1.
7. The GaN-based semiconductor laser device according to claim 4 , wherein
said first relaxation oscillation frequency fr 1 and said second relaxation oscillation frequency fr 2 satisfy a relational expression of (fr 1 −fr 2 )/fr 2 >0.1.
8. The GaN-based semiconductor laser device according to claim 2 , wherein
said first and second striped structures are between two regions, with said n-electrode being in one of two regions.
9. The GaN-based semiconductor laser device according to claim 8 , further comprising:
another n-electrode in the other of said two regions.
10. The GaN based semiconductor laser device according to claim 1 , wherein
said trench has a width that is increased adjacent a luminous region of said laser device.
11. The GaN-based semiconductor laser device according to claim 10 , wherein
said first relaxation oscillation frequency fr 1 and said second relaxation oscillation frequency fr 2 satisfy a relational expression of (fr 1 −fr 2 )/fr 2 >0.1.
12. The GaN-based semiconductor laser device according to claim 1 , wherein
said first relaxation oscillation frequency fr 1 and said second relaxation oscillation frequency fr 2 satisfy a relational expression of (fr 1 −fr 2 )/fr 2 >0.1.
13. The GaN-based semiconductor laser device according to claim 12 , wherein
said first relaxation oscillation frequency fr 1 and said second relaxation oscillation frequency fr 2 satisfy a relational expression of (fr 1 −fr 2 )/fr 2 >0.6.
14. The GaN-based semiconductor laser device according to claim 1 , wherein
said first striped structure is to emit a first light having a first wavelength, and said second striped structure is to emit a second light having a second wavelength, with a difference between the first wavelength and the second wavelength being within 5 nm.
15. The GaN-based semiconductor laser device according to claim 1 , wherein
a ratio of equivalent refractive indexes between a waveguide portion and a peripheral portion of said first striped structure is greater than a ratio of equivalent refractive indexes between a waveguide portion and a peripheral portion of said second striped structure.
16. The GaN-based semiconductor laser device according to claim 1 , wherein
at least one said first and second striped structures has an end face formed by etching.