Semiconductor light source having a reflector
View Patent ↗A reflector is mounted to an outer perimeter of a heat sink holding at least one edge-emitting semiconductor chip, for example a laser diode. The reflector has a shape suitable for gathering light emitted by the laser diodes and redirecting the light in an upward direction away from the heat sink. The reflector can be overmolded onto the heat sink. The reflector can operate by total internal reflection, so that no additional reflector coating step is required. Injection molding of the reflectors onto the heat sink holding the laser diodes enables mass production of powerful yet inexpensive laser light sources.
1. A method of manufacturing a light source, comprising:
(a) providing a heat sink having an outer perimeter, and a plurality of semiconductor chips each having a first edge for emitting light;
(b) mounting the plurality of semiconductor chips flat on the heat sink proximate the outer perimeter of the heat sink, the first edges of the plurality of semiconductor chips facing outwards;
(c) injection molding a reflector out of a thermoplastic material, the reflector comprising a reflecting surface;
(d) mounting the reflector to the outer perimeter of the heat sink so that the reflecting surface is disposed for redirecting light emitted from the first edges to propagate substantially perpendicular to the plurality of semiconductor chips, wherein step (c) is performed before, or simultaneously with, step (d); and
(e) optically coupling the reflector to the first edges of the plurality of semiconductor chips.
2. The method of claim 1 , wherein step (d) includes overmolding the reflector made in step (c) to the heat sink.
3. The method of claim 1 , wherein step (e) includes overmolding an index matching material over the plurality of semiconductor chips, for optically coupling the reflector to the first edges of the plurality of semiconductor chips, and for environmental protection of the plurality of semiconductor chips.
4. The method of claim 1 , wherein in step (d), the molded reflector has an index of refraction sufficiently high for total internal reflection of the emitted light.
5. The method of claim 4 , wherein the heat sink has a round shape, and the reflector has a ring shape having inner and outer perimeters, the reflecting surface extending therebetween, wherein the inner perimeter of the reflector matches the outer perimeter of the heat sink;
wherein in step (d), the reflector is mounted along the inner perimeter thereof to the outer perimeter of the heat sink.
6. The method of claim 5 , wherein in step (e), the reflector is optically coupled to the first edge of each of the semiconductor chips by placing an optical index-matching material between each first edge and the reflector.
7. A light source comprising:
a round heat sink having an outer perimeter;
a plurality of laser diode chips each having a first edge for emitting light, wherein each laser diode chip is disposed flat on the heat sink proximate the outer perimeter thereof, the first edges of the plurality of laser diode chips facing outwards; and
a ring-shaped reflector having inner and outer perimeters and a reflecting surface extending therebetween, the inner perimeter matching the outer perimeter of the heat sink, wherein the ring-shaped reflector is affixed along the inner perimeter thereof to the outer perimeter of the heat sink and optically coupled to the first edges of plurality of laser diode chips so that the reflecting surface is disposed for redirecting light emitted from the first edges to propagate substantially perpendicular to the plurality of laser diode chips,
wherein the reflector comprises a material having a refractive index of 1.45 or higher, for total internal reflection of the emitted light at the reflecting surface.
8. The light source of claim 7 , wherein the plurality of laser diode chips includes at least three laser diode chips.
9. The light source of claim 7 , wherein the reflector comprises an injection-moldable thermoplastic material.
10. The light source of claim 7 , wherein the reflecting surface comprises a concave surface selected from the group consisting of conical, ellipsoidal, hyperbolic, and logarithmic spiral surface.
11. The light source of claim 10 , wherein the plurality of laser diode chips are disposed in equiangular increments.
12. The light source of claim 10 , wherein the reflector comprises a refractive and/or a diffractive element or surface for modifying an angular distribution of the light emitted by the plurality of the semiconductor chips.
13. The light source of claim 10 , further comprising an index matching material disposed between the emitting edges of the plurality of laser diode chips and the reflector, for optical coupling therebetween.
14. The light source of claim 13 , wherein the index matching material comprises a thermoplastic material, wherein the thermoplastic material encapsulates the laser diode chips.