JPH0447979Y2 - - Google Patents

Description

[Detailed explanation of the idea] (b) Industrial application fields The present invention relates to a high-power semiconductor laser.

(B) Prior Art Currently, high-power semiconductor lasers have a structure in which one of a pair of resonator end faces is coated with a high reflection film and the other is coated with a low reflection film.

For example, the International Journal of Quantum Electronics (IEEE
JOURNAL OF QUANTUM
ELECTRONICS), VOL.QE−21, NO.6,
JUNE 1985 P623-P628 has one resonator end face with Al ₂ O ₃ (aluminum oxide) layer and Si (silicon) layer.
A high-power semiconductor that is coated with a high-reflection film with a reflectance of 96% made by laminating multiple layers alternately, and the other cavity end face is coated with a low-reflection film with a reflectance of 4% made of Al ₂ O ₃ . A laser is disclosed.

In addition, as another example of the above-mentioned high reflection film,
There is one in which an insulating film made of SiO ₂ (silicon dioxide), Al ₂ O ₃ , Si ₃ N ₄ (silicon nitride), etc. is formed, and an Au (gold) film is formed on the insulating film.

(c) Problems that the invention aims to solve: However, the former highly reflective film requires precise control of the thickness of each layer, which poses problems in terms of reproducibility. In addition, this structure has poor heat dissipation properties and is therefore unsuitable for high-output semiconductor lasers that generate a lot of heat.

On the other hand, in the latter structure, since the Au film is conductive, there is a risk of an electrical short circuit.

(d) Means for solving the problems The present invention was devised in view of this point, and its structural feature is that one of the end faces of the resonator is coated with a TiN (titanium nitride) film.

(E) Effect Since the TiN film has high thermal conductivity and high optical reflectance, it is ideal as a highly reflective film for high-power semiconductor lasers.

(f) Example Figure 1 shows an example of the present invention, and 1 is a P-type
A substrate made of GaAs, 2 is a current confinement layer made of N-type GaAs laminated on one main surface of the substrate,
A V-shaped groove reaching the substrate 1 from the surface of the constriction layer extends in a direction perpendicular to the plane of the paper in FIG. 1a. 3 is a first cladding layer laminated on the constriction layer 2 and the groove, and the cladding layer has a carrier concentration of 5×10 ¹⁷
It consists of P-type Ga _0.5 Al _0.5 As with a thickness of ~3×10 ¹⁸ /cm ³ , and the layer thickness is 1 to 2 μm at the top of the groove, and the thickness is 1 to 2 μm in the other parts.
It is 0.1-0.3 μm. Reference numeral 4 denotes an active layer laminated on the first conventional layer 3, and the active layer is made of non-doped Ga _0.85 Al _0.15 As with a carrier concentration of 10 ¹⁵ to 10 ¹⁶ /cm ^{3 .}
The layer thickness is 0.05 to 0.1 μm. 5 is a second clad layer laminated on the active layer 4, and the clad layer has a carrier concentration of 1 to 3×
It is made of N-type Ga _0.5 Al _0.5 As of 10 ¹⁸ /cm ³ and has a layer thickness of 1 to 2 μm. Reference numeral 6 denotes a cap layer laminated on the second cladding layer 5, and the cap layer is made of N-type GaAs having a carrier concentration of 10 ¹⁷ /cm ^{3 or} more.
7 is a low-reflection film formed on one of the resonator end faces P, and the low-reflection film is made of Al ₂ O ₃ and has a layer thickness that is an integral multiple of λ/4 (λ is the wavelength of the oscillation laser beam). Its reflectance is about 4%. 8 is a high reflection film formed on the other resonator end face Q, and the high reflection film is made of TiN.

Figure 2 shows the optical reflectance, thermal conductivity, and Pickers hardness of a TiN film, a film made by alternately laminating Al ₂ O ₃ and Si, and a film made by laminating Au on Al ₂ O ₃ . show.

As is clear from Figure 2, the reflectance of the TiN film is
Film formed by alternately laminating Al ₂ O ₃ and Si and Al ₂ O ₃
Although it is slightly lower than a film made by laminating Au on top,
It has a high reflectance of 80% and also has a specific resistance.
Because it is high at 250μΩ・cm, a highly reflective film can be obtained with a single layer.
Therefore, it is suitable for mass production, and since the thermal conductivity of the TiN film is higher than that of other films, it is suitable for high-power semiconductor lasers. Furthermore, since the Pickkers hardness is higher than other films, the end surface is less likely to be damaged.

Incidentally, such a TiN film can be produced under the following conditions: sputtering gas: Ar, input power: 200 to 300 W, sputtering pressure: 2 to 4 × 10 ^-2 (Torr), target: TiN powder, and substrate temperature: ~200°C. It can be formed by sputtering.

Figure 3 shows the optical output-current characteristic A of the device of this embodiment and the optical output-current characteristic B of the conventional device using a film made by alternately laminating multiple layers of Al ₂ O ₃ and Si as a high reflection film.
and

As is clear from FIG. 3, the maximum optical output of the device of this embodiment is higher.

Further, FIG. 4 shows the life characteristic A of the device of this embodiment and the life characteristic B of the conventional device. The life characteristics were determined by measuring the change in drive current over time when a continuous output of 40 mW was applied from the low reflection film side in a high temperature atmosphere of 60°C.

As is clear from FIG. 4, in the conventional device, the driving current increases after 1200 hours or more, whereas in the device of this embodiment, no change in the driving current is observed even after 2000 hours.

(G) Effects of the invention By forming the high-reflection film that covers one cavity end face of a high-power semiconductor laser with a TiN film as in the present invention, it is possible to achieve high output and long life, and also to achieve high output with a single layer. Since a reflective film can be obtained, it is suitable for mass production.

[Brief explanation of the drawing]

Fig. 1 shows an embodiment of the present invention, Fig. 1a is a sectional view taken along line A-A' in Fig.
-B' line sectional view, FIG. 2 is a diagram showing physical characteristics of each high reflection film, and FIGS. 3 and 4 are characteristic diagrams showing optical output-current characteristics and life characteristics, respectively. 8...TiN film, P, Q...resonator end face.

Claims (1)

[Scope of utility model registration request] A high-power semiconductor laser characterized by having one of a pair of cavity end faces coated with a TiN film.