Fault tolerant laser diode package
View Patent ↗A laser diode package ( 10 ) according to the present invention is tolerant of short-circuit and open-circuit failures. The laser diode package ( 10 ) includes a laser diode bar ( 12 ), a forward-biased diode ( 14 ), a heat sink ( 18 ), and a lid ( 16 ) which may have fusible links ( 86 ). The laser diode bar ( 12 ) and the forward-biased diode ( 14 ) are electrically connected in parallel between the heat sink ( 18 ) and the lid ( 16 ). The emitting region of the laser diode bar ( 12 ) is aligned to emit radiation away from the forward-biased diode ( 14 ). Several packages can be stacked together to form a laser diode array ( 42 ). The forward-biased diode ( 14 ) allows current to pass through it when an open-circuit failure has occurred in the corresponding laser diode bar ( 12 ), thus preventing an open-circuit failure from completely disabling the array ( 42 ). The fusible links ( 86 ), if used on the lid ( 16 ), prevent damaged active regions ( 90 ) in a laser diode bar ( 12 ) from short-circuiting and drawing more electrical current than the other active regions ( 90 ).
1. A laser diode package, comprising:
a heat sink, said heat sink having a top end;
a lid;
a laser diode bar positioned between said heat sink and said lid, said laser diode bar producing energy in response to current being conducted in a direction from said heat sink to said lid, said laser diode bar having an emitting surface that is positioned within 0.001 inches of said top end of said heat sink; and
a forward-biased diode positioned between said heat sink and said lid, said forward-biased diode being arranged to conduct current from said heat sink to said lid in response to an open-circuit failure in said laser diode bar, said forward-biased diode having a turn-on voltage in the direction of said current that is greater than a turn-on voltage in the direction of said current of said laser diode bar under normal operating conditions;
a first continuous solder layer on said heat sink such that said solder layer joins said heat sink to said forward-biased diode and said laser diode bar, said first continuous solder layer is a pretinned layer of solder located on a plurality of surfaces of said heat sink; and
a second continuous solder layer on said lid such that said solder layer joins said lid to said forward-biased diode and said laser diode bar, said second continuous solder layer is a pretinned layer of solder located on a plurality of surfaces of said lid.
2. The laser diode package of claim 1 , wherein a turn-on voltage for said forward-biased diode is greater than said turn-on voltage of said laser diode bar by less than 1 Volt.
3. The laser diode package of claim 1 , wherein said forward-biased diode is made from a semiconductor material, said semiconductor material including a substrate with epitaxial layers.
4. The laser diode package of claim 3 , wherein said semiconductor material is made from gallium arsenide.
5. The laser diode package of claim 3 , wherein said substrate with said epitaxial layers results in an equivalent circuit of two diodes in series.
6. The laser diode package of claim 1 , wherein said heat sink is made from an electrically conductive material.
7. The laser diode package of claim 1 , wherein said lid is approximately the same height as said heat sink.