Optical semiconductor device, laser chip and laser module

Abstract

An optical semiconductor device has a semiconductor substrate, an optical semiconductor region and a heater. The optical semiconductor region is provided on the semiconductor substrate and has a width smaller than that of the semiconductor substrate. The heater is provided on the optical semiconductor region. The optical semiconductor region has a cladding region, an optical waveguide layer and a low thermal conductivity layer. The optical waveguide layer is provided in the cladding region and has a refractive index higher than that of the cladding region. The low thermal conductivity layer is provided between the optical waveguide layer and the semiconductor substrate and has a thermal conductivity lower than that of the cladding region.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

Preferred embodiments of the present invention will be described in detail with reference to the following drawings, wherein:

FIG. 1 illustrates a cross sectional view of a distributed reflector in accordance with a first embodiment of the present invention;

FIG. 2A and FIG. 2B illustrate a relationship between composition and a property of In_1-xGa_xAs_yP_1-y;

FIG. 3 illustrates a relationship between composition and a refractive index of In_1-x-yAl_xGa_yAs;

FIG. 4 illustrates a relationship between composition and a refractive index of In_1-xAl_xAs_yP_1-y;

FIG. 5 illustrates a perspective view of a semiconductor laser chip in accordance with a second embodiment of the present invention;

FIG. 6A illustrates a top view of a semiconductor laser chip;

FIG. 6B illustrates a cross sectional view taken along a line A-A of FIG. 6A;

FIG. 7 illustrates an overall structure of a laser module in accordance with a third embodiment of the present invention; and

FIG. 8 illustrates an overall structure of a laser module in accordance with a fourth embodiment of the present invention.

Claims

1. An optical semiconductor device comprising: a semiconductor substrate;an optical semiconductor region that is provided on the semiconductor substrate and has a width smaller than that of the semiconductor substrate; anda heater that is provided on the optical semiconductor region,the optical semiconductor region having a cladding region, an optical waveguide layer and a low thermal conductivity layer,the optical waveguide layer being provided in the cladding region and having a refractive index higher than that of the cladding region,the low thermal conductivity layer being provided between the optical waveguide layer and the semiconductor substrate and having a thermal conductivity lower than that of the cladding region.

2. The optical semiconductor device as claimed in claim 1, wherein the low thermal conductivity layer is provided on overall in a width direction of the optical semiconductor region.

3. The optical semiconductor device as claimed in claim 1, wherein the low thermal conductivity layer is composed of a material having a thermal conductivity lower than 1/10 of that of the cladding region.

4. The optical semiconductor device as claimed in claim 1, wherein the low thermal conductivity layer is composed of a material having a refractive index lower than that of the optical waveguide layer.

5. The optical semiconductor device as claimed in claim 1, wherein the low thermal conductivity layer is composed of a material having a refractive index under 106% of the refractive index of the cladding region.

6. The optical semiconductor device as claimed in claim 1, wherein the low thermal conductivity layer is composed of a semiconductor crystal having more than one congener.

7. The optical semiconductor device as claimed in claim 6, wherein: the cladding region is composed of InP; andthe semiconductor crystal is composed of InGaAsP, InAlGaAs or InAlAsP.

8. The optical semiconductor device as claimed in claim 7, wherein the InGaAsP semiconductor crystal is substantially lattice matched to the InP and has As so that As composition against P is more than 15% and is less than 55%.

9. The optical semiconductor device as claimed in claim 7, wherein the InAlGaAs semiconductor crystal is substantially lattice matched to the InP and has Al so that Al composition against InGa is more than 26%.

10. The optical semiconductor device as claimed in claim 1 further comprising a cladding region provided between the optical waveguide layer and the low thermal conductivity layer.

11. A semiconductor laser chip comprising: an optical semiconductor device having a semiconductor substrate, an optical semiconductor region and a gain region;the optical semiconductor region being provided on the semiconductor substrate and having a width smaller than that of the semiconductor substrate,the heater being provided on the optical semiconductor region,the optical semiconductor region having a cladding region, an optical waveguide layer and a low thermal conductivity layer,the optical waveguide layer being provided in the cladding region and having a refractive index higher than that of the cladding region,the low thermal conductivity layer being provided between the optical waveguide layer and the semiconductor substrate and having a thermal conductivity lower than that of the cladding region,the gain region being provided on the semiconductor substrate and being optically coupled to the optical waveguide layer.

12. The semiconductor laser chip as claimed in claim 11, wherein the gain region has a width larger than that of the optical semiconductor region.

13. The semiconductor laser chip as claimed in claim 11 further comprising an optical intensity controller that is optically coupled to the optical waveguide layer and the gain region and that absorbs or amplifies a light.

14. A laser module comprising: a semiconductor laser chip having an optical semiconductor device, a gain region and a temperature control device;the optical semiconductor device having a semiconductor substrate, an optical semiconductor region and a heater,the optical semiconductor region being provided on the semiconductor substrate and having a width smaller than that of the semiconductor substrate,the heater being provided on the optical semiconductor region,the optical semiconductor region having a cladding region, an optical waveguide layer and a low thermal conductivity layer,the optical waveguide layer being provided in the cladding region and having a refractive index higher than that of the cladding region,the low thermal conductivity layer being provided between the optical waveguide layer and the semiconductor substrate and having a thermal conductivity lower than that of the cladding region,the gain region being provided on the semiconductor substrate and being optically coupled to the optical waveguide layer,at least a part of the semiconductor laser chip being arranged on the temperature control device,the temperature control device controlling the temperature of at least a part of the semiconductor laser chip.

15. The laser module as claimed in claim 14, wherein at least the gain region is arranged on the temperature control device.

16. The laser module as claimed in claim 14, wherein whole of the semiconductor laser chip is arranged on the temperature control device.