US2021288462A1PendingUtilityA1
System For Optimizing A Laser
Est. expiryMar 13, 2037(~10.7 yrs left)· nominal 20-yr term from priority
H01S 3/1396H01S 3/2232H01S 3/137H01S 3/08009H01S 3/1394H01S 3/1305
68
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Claims
Abstract
A system for producing single-frequency or near-single-frequency operation of a laser beam includes a laser for emitting a laser beam at each one of a plurality of cavity lengths, A detector is configured to receive at least a portion of the laser beam emitted, and generate a signal. A computer system is configured to identify at least one beat note in the signal for each of at least one of the plurality of cavity lengths, the at least one beat note indicating the presence of one or more higher-order transverse modes, longitudinal modes, or both, in the received at least the portion of the laser beam emitted at the at least one of the plurality of cavity lengths. The cavity is adjusted to one of the plurality of cavity lengths for eliminating or minimizing the at least one beat note.
Claims
exact text as granted — not AI-modifiedWe claim:
1 . A method for producing single-frequency operation of a laser beam generated by a laser beam system, comprising:
providing a laser for emitting a laser beam within a laser beam cavity, the cavity having a length, wherein the length of the cavity may be adjusted to one of a plurality of cavity lengths; emitting the laser beam at each one of the plurality of cavity lengths; providing a detector, operably coupled to a computer, for:
receiving at least a portion of the laser beam emitted at each one of the plurality of cavity lengths; and
detecting the presence of transverse modes, longitudinal modes, or both, in the received laser beam emitted at each one of the plurality of cavity lengths and when at least transverse modes, longitudinal modes, or both, are detected, generating at least one laser beam signal having a beat-note indicative thereof;
selecting, based upon the generated at least one laser beam signals, at least one cavity lengths for eliminating the beat-note and producing single-frequency operation of the laser beam; and adjusting the length of the cavity one of the one or more selected cavity lengths.
2 . The method of claim 1 , wherein the detecting of the presence of transverse modes, longitudinal modes, or both, comprises detecting a frequency difference of the transverse modes, the longitudinal modes, or both.
3 . The method of claim 2 , wherein the frequency difference comprises the difference between transverse modes across approximately one free spectral range within the cavity.
4 . The method of claim 3 , wherein the frequency difference ν map may be determined using the formula:
2
π
L
c
υ
m
n
p
-
(
m
+
n
+
1
)
(
ψ
(
z
2
)
-
ψ
(
z
1
)
)
=
p
π
,
where
L=z 2 −z 1 is the length of the cavity,
ψ(z)=arctan(z/z r ) is the Gouy phase shift,
z r is the Rayleigh length of the emitted laser beam,
(m, n) are the transverse mode indices, and
p is the longitudinal mode index.
5 . The method of claim 1 , wherein the method further comprises calculating a mode purity value by combining a detected amplitude of the beat-note in the generated laser beam signal (AC portion) with a detected intensity of the generated laser beam signal (DC portion), and adjusting the length of the cavity to the highest mode purity value.
6 . The method of claim 5 , wherein calculating the mode purity value comprises determining a ratio R of the detected intensity of the generated laser beam signal (DC portion) with respect to the amplitude of the detected beat-note in the generated laser beam signal (AC portion) defined as one of:
R
=
Vave
Vpp
where V ave is the average voltage and V pp is peak-to-peak voltage;
R
=
V
a
v
e
V
R
M
S
where V ave is the average voltage and V RMS is the root mean square of the voltage; or
R
=
V
a
v
e
V
σ
where V ave is the average voltage and V σ is the standard deviation of the voltage.
7 . The method of claim 5 , wherein the highest mode purity value may comprise the length of cavity wherein the amplitude of the generated laser beam signal is the weakest and the intensity of the generated laser beam signal is the strongest.
8 . The method of claim 1 , wherein the adjusting the length of the cavity to one of the one or more selected cavity lengths is performed in real-time to maintain single-frequency operation of the laser.
9 . A laser beam system for producing single-frequency operation of a laser, the laser system comprising:
a laser for emitting a laser beam, the laser beam emitted in a laser cavity having a first end and a second end, and having a length, the cavity comprising at least,
a diffraction grating, positioned at the first end of the cavity, for providing a mirror within the cavity;
an output coupler, positioned at the second end of the cavity, wherein the distance between the diffraction grating and the output coupler defines the length of the cavity, and
a gain medium, positioned between the diffraction grating and the output coupler,
a laser beam splitter for receiving and dividing the emitted laser beam and for directing at least a portion of the divided laser beam to a laser beam detector, a laser beam detector, for receiving and detecting the directed portion of the emitted laser beam from the laser beam splitter, and for generating at least one signal indicative thereof, an actuator, for actuating at least the diffraction grating, the output coupler, or both, to adjust the length of the cavity to produce a single-frequency operation of the laser.
10 . The system of claim 9 , wherein the diffraction grating can be rotatable about an axis x for selecting a particular frequency of the emitted laser beam.
11 . The system of claim 10 , wherein the particular frequency comprises a mixture of frequencies.
12 . The system of claim 11 , wherein the mixture of frequencies comprises at least a fundamental mode and a plurality of high-order transverse modes.
13 . The system of claim 9 , wherein the detector comprises a bandwidth in the order of at least one free spectral range of the cavity.
14 . The system of claim 13 , wherein the detector comprises a photodetector.
15 . The system of claim 9 , wherein the actuator comprise a piezoelectric actuator.
16 . The system of claim 15 , wherein the actuator may be controlled by a piezo driver.Join the waitlist — get patent alerts
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