Method for active stabilizatiion of an injection locked laser with an optical bandpass filter
A high-power single-frequency laser system and a method for implementing the same. The system and method require only a photodetector ( 110 ) and a narrow optical bandpass filter ( 108 ) to probe the spectral mode of slave laser ( 106 ), no additional bulky devices are required. The photodetector ( 110 ) and narrow optical bandpass filter ( 108 ) can be easily integrated into the beam path. The spectral mode of slave laser ( 106 ) is monitored through the reflected signal from the narrow-laser line filter ( 108 ), which is neither sensitive to beam alignment nor bandwidth limited. As a result, high spectral mode purity and low intensity noise of the slave laser ( 106 ) can be simultaneously obtained. The slave laser ( 106 ) can be locked even when the master laser ( 102 ) frequency is dynamically scanned over GHz range. The system and method can be applied in laser cooling and trapping of atoms towards degenerate dipolar quantum gases.
1 . A high-power single-frequency laser system, comprising:
a master laser configured for producing a seeding beam;
an optical isolator optically coupled with the master laser and configured for directing the seeding beam;
a slave laser optically coupled with the optical isolator and configured for receiving the directed seeding beam and producing an injection-locked beam;
an optical bandpass filter inserted between the optical isolator and the slave laser, and configured for selectively filtering a signal beam from the directed seeding beam;
a photodetector optically coupled with the optical bandpass filter and configured for probing the signal beam;
a proportional-integral-derivative (PID) controller electrically connected to the photodetector and configured for producing an output voltage based on a probing signal from the photodetector;
a current controller electrically connected to the PID controller and the slave laser and configured for regulating a current supplied to the slave laser based on the output voltage produced by the PID controller; and
wherein the current supplied to the slave laser is actively controlled with a side-of-fringe scheme to stabilize a transmission power of the slave laser.
2 . The high-power single-frequency laser system according to claim 1 , further comprising a pair of mirrors inserted between the mater laser and the optical isolator, and configured for aligning the seeding beam.
3 . The high-power single-frequency laser system according to claim 2 , further comprising a pair of prims inserted between the slave laser and the optical bandpass filter, and configured for shaping beam profile of the injection-locked beam.
4 . The high-power single-frequency laser system according to claim 3 , further comprising a half-wave plate inserted between the slave laser and the pair of prims, and configured for adjusting the polarization of the injection-locked beam.
5 . The high-power single-frequency laser system according to claim 1 , wherein the master laser is a tunable external cavity diode laser.
6 . The high-power single-frequency laser system according to claim 1 , wherein the optical isolator is a polarization dependent isolator.
7 . The high-power single-frequency laser system according to claim 1 , wherein the slave laser is a laser diode.
8 . The high-power single-frequency laser system according to claim 1 , wherein the optical bandpass filter is a laser-line filter having a full width at half maximum of 1.5 nm.
9 . The high-power single-frequency laser system according to claim 1 , wherein the photodetector is a Silicon amplifier photodetector.
10 . A method for implementing a high-power single-frequency laser source, comprising:
producing, by a master laser, a seeding beam; optically coupling an optical isolator with the master laser and configuring the optical isolator to direct the seeding beam;
optically coupling a slave laser with the optical isolator and configuring the slave laser to receive the directed seeding beam and produce an injection-locked beam;
inserting an optical bandpass filter between the optical isolator and the slave laser, and configuring the optical bandpass filter to selectively filter a signal beam from the directed seeding beam;
optically coupling a photodetector with the optical bandpass filter and configuring the photodetector to probe the signal beam;
electrically connecting a proportional-integral-derivative (PID) controller to the photodetector and configuring the PID controller to produce an output voltage based on a probing signal from the photodetector; and
electrically connecting a current controller to the PID controller and the slave laser and configuring the current controller to regulate a current supplied to the slave laser based on the output voltage produced by the PID controller; and
wherein the slave laser is actively controlled with a side-of-fringe scheme to stabilize a transmission power of the slave laser.
11 . The method according to claim 10 , further comprising inserting a pair of mirrors between the mater laser and the optical isolator, and configuring the pair of mirrors to aligning the seeding beam.
12 . The method according to claim 11 , further comprising inserting a pair of prims between the slave laser and the optical bandpass filter, and configuring the pair of prims to shape a beam profile of the injection-locked beam.
13 . The method according to claim 12 , further comprising inserting a half-wave plate between the slave laser and the pair of prims, and configuring the half-wave plate to adjust the polarization of the injection-locked beam.
14 . The method according to claim 10 , wherein the master laser is a tunable external cavity diode laser.
15 . The method according to claim 10 , wherein the optical isolator is a polarization dependent isolator.
16 . The method according to claim 10 , wherein the slave laser is a laser diode.
17 . The method according to claim 10 , wherein the optical bandpass filter has a full width at half maximum of 1.5 nm.
18 . The method according to claim 10 , wherein the photodetector is a Silicon free-space amplifier photodetector.