Tyson Lin

Generation of azimuthally and radially polarized off-axis beams with an intracavity large-apex-angle axicon

Depending on cavity configuration, a c-cut Nd:YVO4 laser by using a large-apex-angle axicon can execute azimuthally and radially polarized operations. A large-apex-angle axicon dominates and stabilizes the generation of the pattern, and expands the difference between the ordinary and extraordinary rays to generate off-axis cylindrical vector beams. When the cavity length is properly adjusted, the polarization of off-axis laser beams can exhibit a transition from azimuthal to radial polarization. The degree of polarizations can be up to 95.4% ± 2.6% and 94% ± 3.7% for azimuthally and radially polarized beams, respectively; and the slope efficiencies are approximately 20.5% for both polarized operations. Using two-pass-mode ray tracing, the ray generating mechanisms and divergent angles of their patterns were analyzed.

A compact iodine-stabilized HeNe laser and crossover resonances at 543 nm

Abstract We have constructed a compact iodine-stabilized 543 nm HeNe laser using the third-harmonic locking technique. From the signal-to-noise ratio, the noise-limited-stability would be better than 1×10 −12 for integration time >1 s. Moreover, several crossover resonances of R(12) 26–0 line are investigated and identified. Two crossover resonances are found adjacent to the hyperfine component a 9 , the recommended wavelength standard. Instead, we suggest the hyperfine component b 10 of R(106) 28–0 line as the wavelength standard for the absence of neighboring main lines or crossover resonances.

Iodine-stabilized 543 nm HeNe lasers

Abstract Internal-mirror 543 nm HeNe lasers are frequency-stabilized on the iodine hyperfine transitions. The Allen standard deviation of 1×10 −12 is reached after a 10 second integration time. The hyperfine spectrum originating from the R (12) 26-0 and R (106) 28-0 lines of the B-X system of 127 I 2 has been studied. The frequency differences between hyperfine components have been measured by beat frequency techniques, and the hyperfine coupling constants are fitted for the R (106) 28-0 line.

Modulation-free laser frequency stabilization to molecular absorption using single acoustooptic frequency shifter

A modulation-free scheme for the laser frequency stabilization to molecular transitions is demonstrated in this letter. In this scheme, two diffracted beams of opposite order from a single acoustooptic frequency shifter were used to simultaneously probe the Doppler-broadened absorption of acetylene. A dispersion-like (DL) signal was obtained from the difference of the two absorption signals. By carefully balancing the two absorption signals, the deviation of the center of the DL signal from the center of Doppler-limited absorption can be less than 2.4 MHz. Using the DL signal as the error signal for frequency stabilization, we could lock a 1.53-/spl mu/m external-cavity diode laser with an estimated stability of 3.1/spl times/10/sup -10/.

CO 2 laser frequency stabilization using the radio-frequency optogalvanic Lamb dip

The Lamb dip of the CO(2) saturation signal in an extracavity low-pressure CO(2)-N(2) rf glow discharge is detected optogalvanically and used to stabilize the frequency of a CO(2) laser. The frequency stability is estimated to be better than 100 kHz.

Iodine stabilization of a diode laser in the optical communication band

The iodine molecule has frequently been used as a frequency reference from the green to the near-infrared wavelength region (500-900 nm). We describe the frequency locking of the second-harmonic signal of a 197.2-THz (1520.25-nm) distributed-feedback diode laser to the absorption lines of the iodine hyperfine structure; a frequency jitter below 0.1 MHz was achieved at a 300-ms time constant. This scheme provides a simple, compact, and high-performance frequency reference in the optical communication band.

Two-Mode Frequency Stabilization of an Internal-Mirror 1.523-µm He-Ne Laser

We studied the polarization properties of a short internal-mirror 612 nm He-Ne laser. We found that polarization flip did not occur at the symmetric two-mode location but near the center of the power profile. Therefore, the laser could be frequency-stabilized using the two-mode method, and the stability achieved was better than 5 × 10 ‐10 . This laser can be used as a light source in length measurements using multi-color interferometers.

Polarization Properties of an Internal-Mirror 543.5-nm HeNe Laser

The polarization properties of an internal-mirror 543.5-nm HeNe laser are investigated. The polarization properties under magnetic fields are quite different from those of red HeNe lasers. The polarization flip can be eliminated by applying a transverse or axial magnetic field, and this elimination is useful in two-mode frequency stabilization.

Frequency stabilization and measurements of 543 nm HeNe lasers

In this paper we report our investigations on the frequency stabilization and frequency measurements of 543 nm HeNe laser. It contains following four different works. (1) Using a metal laser tube we have built an iodine-stabilized 543 nm HeNe laser by the Frequency-Modulation (FM) spectroscopy. The signal-to-noise ratio of the hyperfine spectrum reached 2 × 10−12 at 1 s sampling time. (2) We have built a compact iodine-stabilized 543 nm HeNe laser system using the third-harmonic locking technique. Stability better than 1 × 10−12 for sampling time >1 s is obtained. We also suggest the b10 line for the future recommendation. (3) We constructed the Lamb-dip stabilized He-20Ne and He-22Ne lasers and measured their frequency stability, reproducibility, and absolute frequencies. The results suggest that the Lamb-dip stabilized lasers are appropriate for secondary wavelength standards. We have also deduced the isotope shift of Ne atom at 543 nm. (4) We have developed two two-mode stabilized 543 nm HeNe lasers using the bang-bang control method. The Allan variance is 1 × 10−11 at 1 s sampling time.

Diode Laser Frequency Locking to an Etalon With a Double-Pass Acousto-Optic Frequency Shifter

We demonstrate an optical heterodyne spectroscopy on the reflection of an etalon using a double-pass acousto-optics frequency shifter. The experiment setup is a modified Michelson interferometer using the double-pass acousto-optics frequency shifter as the beam splitter and one etalon as the end mirror. Without using frequency modulation, the dispersion-like signal of the etalon reflection was successfully observed and optimized. Using the dispersion-like signal as an error signal, we locked a 780-nm external cavity diode laser to one resonant mode of the etalon. The estimated relative stability was ~2.6 × 10-10 in 0.16-s integration time.