Semiconductor laser, operating method for a semiconductor laser, and method for determining the optimum fill factor of a semiconductor laser

Patent metadata

Field	Value
Publication number	US-11942763-B2
Application number	US-201816954961-A
Country	US
Kind code	B2
Filing date	Dec 14, 2018
Priority date	Dec 19, 2017
Publication date	Mar 26, 2024
Grant date	Mar 26, 2024

Abstract

In one embodiment, the semiconductor laser (1) comprises a semiconductor layer sequence (2) based on the material system AlInGaN with at least one active zone (22) for generating laser radiation. A heat sink (3) is thermally connected to the semiconductor layer sequence (2) and has a thermal resistance towards the semiconductor layer sequence (2). The semiconductor layer sequence (2) is divided into a plurality of emitter strips (4) and each emitter strip (4) has a width (b) of at most 0.3 mm in the direction perpendicular to a beam direction (R). The emitter strips (4) are arranged with a filling factor (FF) of less than or equal to 0.4. The filling factor (FF) is set such that laser radiation having a maximum optical output power (P) can be generated during operation.

First claim

The invention claimed is:

1. A semiconductor laser comprising:
a semiconductor layer sequence on a basis of a material system AlInGaN with at least one active zone, and
at least one heat sink to which the semiconductor layer sequence is thermally connected and to which the semiconductor layer sequence has a thermal resistance,
wherein the semiconductor layer sequence is divided into a plurality of emitter strips and each emitter strip has a width between 15 μm and 150 μm inclusive in a direction perpendicular to a beam direction, the emitter strips are arranged with a filling factor (FF) of between 0.07 and 0.18 inclusive and the filling factor (FF) is a quotient of a width b of the emitter strips and a periodicity N of the emitter strips,
the semiconductor layer sequence is attached by a solder to the heat sink and the solder extends over an entire surface and uninterruptedly between the semiconductor layer sequence and the at least one heat sink, and
the semiconductor layer sequence is located on a growth substrate thereof and the growth substrate is located on a side of the semiconductor layer sequence facing away from the heat sink,
wherein the following applies to the filling factor (FF) as a function of thermal resistance Rth:
FF =(0.18 W 2 /K 2 Rth 2 −0.40 W/K Rth+ 0.30)±0.02,

wherein each of the emitter strips are each configured as strip waveguides, wherein the at least one active zone is removed between adjacent emitter strips,
wherein the at least one heat sink is attached by a soft solder to the semiconductor layer sequence, wherein the soft solder comprises indium and the at least one heat sink is a microchannel cooler.

2. The semiconductor laser according to claim 1 , wherein the filling factor is between 0.12 and 0.16.

3. The semiconductor laser according to claim 1 , wherein the filling factor is between 0.09 and 0.13 inclusive.

4. The semiconductor laser according to claim 1 , wherein the semiconductor layer sequence comprises at least 12 and at most 80 of the emitter strips.

5. The semiconductor laser according to claim 1 , comprising two heat sinks, wherein on both sides of the semiconductor layer sequence one of the heat sinks is located.

6. The semiconductor laser according to claim 1 , wherein a reflectivity for a generated laser radiation at a coupling-out surface is at least 15% and at most 35%.

7. An operating method for a semiconductor laser according to claim 1 , wherein the semiconductor layer sequence comprising emitter regions that are operated with a target operating current in such a way that a maximum achievable electro-optical conversion efficiency of generated laser radiation results, wherein the target operating current is specified for an average service life of the semiconductor laser of 10,000 h, and wherein optical output power decreases based on an increase in the filling factor, irrespective of a change in the target operating current for a service life of 10,000 h.

8. The operating method according to claim 7 , wherein processing of a material is carried out by means of the semiconductor laser, wherein the material is processed under water and/or the material has a reflectivity for near-infrared radiation of at least 80%, and wherein the optical output power is at least 50 W on average.

9. A semiconductor laser comprising:
a semiconductor layer sequence on a basis of a material system AlInGaN with at least one active zone, and
at least one heat sink to which the semiconductor layer sequence is thermally connected and to which the semiconductor layer sequence has a thermal resistance,
wherein the semiconductor layer sequence is divided into a plurality of emitter strips and each emitter strip has a width between 15 μm and 150 μm inclusive in a direction perpendicular to a beam direction, the emitter strips are arranged with a filling factor (FF) between 0.07 and 0.18 inclusive, and the filling factor (FF) is a quotient of a width b of the emitter strips and a periodicity N of the emitter strips and is set so that laser radiation having a maximum achievable electro-optical conversion efficiency generated during operation,
wherein the following applies to the filling factor (FF) as a function of thermal resistance Rth:
FF =(0.18 W 2 /K 2 Rth 2 −0.40 W/K Rth+ 0.30)±0.02,

wherein each of the emitter strips are each configured as strip waveguides, wherein the at least one active zone is removed between adjacent emitter strips.

10. The semiconductor laser according to claim 9 , wherein the heat sink is attached by soft soldering to the semiconductor layer sequence.

11. The semiconductor laser according to claim 9 , wherein the heat sink is attached by hard soldering to the semiconductor layer sequence.

12. A method for determining an optimum filling factor in a semiconductor laser with a range between 0.07 and 0.18 inclusive, comprising:
A) determining geometric dimensions of a still unstructured semiconductor layer sequence;
B) determining a threshold current density (J s ), a specific surface conductivity (ρ), a steepness (S h ) of a laser characteristic curve and a maximum temperature (T j ) of an active zone of the semiconductor layer sequence;
C) determining and parameterizing a thermal connection of the semiconductor layer sequence to at least one heat sink;
D) inserting determined values into an equation or an equation system for an optical output power (P) and/or for a target operating current (I op ); and
E) determining a filling factor (FF) on a basis of the equation or the equation system taking into account a temperature (T hs ) on a side of the semiconductor layer sequence towards the at least one heat sink, wherein the filling factor (FF) is a quotient of a width b of emitter strips and a periodicity N of the emitter strips,
wherein the filling factor (FF) and a thermal resistance (R th ), which results from the thermal connection of the semiconductor layer sequence to the at least one heat sink, are mutually dependent,
wherein further for an optical power (P) of the semiconductor laser, a threshold current (I s ), an input voltage (U op ), an electrical series resistance (R s ), a length (L) of the emitter strips, a total width (w) of an envelope of the emitter strips, and an optical power loss (P loss ) holds true:
I op =−( U op −Sh )±√{square root over (( U op −Sh ) 2 −4 R s ( I s Sh−T j −T hs /R th ))}/2 R s   (V)

P=Sh ( I op −I s )  (I)

P=R s I op 2 +U op I op −P loss   (II)

T j =T hs +R th P loss   (III)

I s =J s *L*w*FF
R s =ρ/L*w*FF

the optical output power (P) is calculated by inserting the target operating current (I op ) from (V) into (I), the filling factor (FF) is then varied, dependence of laser input parameters results in different results relating to I op and to the output power (P).

Assignees

• Osram Oled Gmbh

Inventors

• König Harald
• Stojetz Bernhard
• Lell Alfred
• Ali Muhammad

Classifications

• H01S5/4031 Primary

  Edge-emitting structures · CPC title

• B23K26/122

  in a liquid, e.g. underwater · CPC title

• H01S5/0237

  by soldering · CPC title

• H01S5/02469

  Passive cooling, e.g. where heat is removed by the housing as a whole or by a heat pipe without any active cooling element like a TEC · CPC title

• H01S5/02492

  CuW heat spreaders · CPC title