Picosecond Q-switched microlasers
AssigneeMassachusetts Institute of Technology
InventorJohn J. Zayhowski
Life of this patent
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Abstract
A Q-switched laser having a gain medium disposed within a first resonant cavity and a second resonant cavity, sharing a common mirror with the first cavity, whose optical length is adjustable such that the quality Q of the first resonant cavity is affected. One aspect of the invention is the selection of the cavity lengths and the reflectivities of the mirrors of the first and second cavity such that Q-switched pulses of less than 100-ps duration can be obtained. Another aspect of the invention is the ability to generate said pulses with peak powers in excess of 100 kW for applications in high-precision optical radar, nonlinear optics, micromachining, microsurgery, and other applications where short pulses with high peak powers are required.
Claims25
A coupled-cavity Q-switched laser system for generating a short pulse of light comprised of a gain medium disposed within a first resonant cavity, a second resonant cavity sharing a common partially reflecting mirror with said first cavity, and a means for changing the relative optical length of the second resonant cavity with respect to the first, said second cavity having an output mirror which provides feedback to said first resonant cavity through said partially reflecting mirror such that by changing said optical length the quality Q of said first resonant cavity is changed, and wherein the reflectivities of the partially reflecting mirror and said output mirror are determined by the following formulas:
- ##EQU5## where .gamma. is in the range from 0.06 to 0.6, R.sub.1 is the reflectivity of said partially reflecting mirror, R.sub.2 is the reflectivity of said output mirror, G.sub.rt is the small-signal round-trip gain of the first cavity at the time the pulse begins to form, m is the ratio of the round-trip time of light in the second cavity to the round-trip time of light in the first cavity, v.sub.l is the lasing frequency, and .delta..sub.1 +.delta..sub. =.delta.(t.sub.rt,et) is the relative change in said optical length induced during Q switching.
A method of forming a coupled-cavity Q-switched laser system for generating a short pulse of light comprising the steps of:
- forming a first resonant cavity containing a laser gain medium and a second resonant cavity sharing a common partially reflecting mirror with said first cavity, and providing a means for changing the relative optical length of the second resonant cavity with respect to the first, said second resonant cavity having an output mirror which provides feedback to said first resonant cavity through said partially reflecting mirror such that by changing said optical length the quality Q of said first resonant cavity is changed, and wherein the reflectivities of the partially reflecting mirror and said output mirror are determined by the following formulas:
- ##EQU6## where .gamma. is in the range from 0.06 to 0.6, R.sub.1 is the reflectivity of said partially reflecting mirror, R.sub.2 is the reflectivity of said output mirror, G.sub.rt is the small-signal round-trip gain of the first cavity at the time the pulse begins to form, m is the ratio of the round-trip time of light in the second cavity to the round-trip time of light in the first cavity, v.sub.l is the lasing frequency, and .delta..sub.1 +.delta..sub.2 =.delta.(t.sub.rt,et) is the relative change in said optical length induced during Q-switching.
A solid-state coupled-cavity Q-switched laser system for generating a short pulse of light comprised of a first resonant cavity formed of a solid-state gain medium having an input facet with an input mirror formed thereon and an output facet with a partially reflecting mirror formed thereon, a second resonant cavity providing optical feedback to the first cavity, said second cavity formed of a second solid-state material with a variable optical length having a front facet disposed adjacent to said partially reflecting mirror and a back facet with an output mirror formed thereon, and a means for controlling the length of said second solid-state material, wherein by changing the optical length of said second solid-state material the quality Q of said first resonant cavity is changed, and wherein the reflectivities of the partially reflecting mirror and said output mirror are determined by the following formulas:
- ##EQU7## where .gamma. is in the range from 0.06 to 0.6, R.sub.1 is the reflectivity of said partially reflecting mirror, R.sub.2 is the reflectivity of said output mirror, G.sub.rt is the small-signal round-trip gain of the first cavity at the time the pulse begins to form, m is the ratio of the round-trip time of light in the second cavity to the round-trip time of light in the first cavity, v.sub.l is the lasing frequency, and .delta..sub.1 +.delta..sub.2 =.delta.(t.sub.rt,et) is the relative change in said optical length induced during Q switching.
A method of forming a solid-state coupled-cavity Q-switched laser system for generating a short pulse of light comprising the steps of:
- forming a first resonant cavity of a solid-state gain medium having an input facet with an input mirror formed thereon and an output facet with a partially reflecting mirror formed thereon and a second resonant cavity to provide optical feedback to the first cavity, said second cavity formed of a second solid-state material with a variable optical length having a front facet disposed adjacent to said partially reflecting mirror and a back facet with an output mirror formed thereon, and providing a means for controlling the length of said second solid-state material, wherein by changing the optical length of said second solid-state material the quality Q of said first resonant cavity is changed, and wherein the reflectivities of the partially reflecting mirror and said output mirror are determined by the following formulas:
- ##EQU8## where .gamma. is in the range from 0.06 to 0.6, R.sub.l is the reflectivity of said partially reflecting mirror, R.sub.2 is the reflectivity of said output mirror, G.sub.rt is the small-signal round-trip gain of the first cavity at the time the pulse begins to form, m is the ratio of the round-trip time of light in the second cavity to the round-trip time of light in the first cavity, v.sub.l is the lasing frequency, and .delta..sub.1 +.delta..sub.2 =.delta. (t.sub.rt,et) is the relative change in said optical length induced during Q switching.
Dependencies are inferred from the claim text.