Shaokai Wang

100-Hz Linewidth Diode Laser With External Optical Feedback

We present a narrow-linewidth diode laser with optical feedback from a high-finesse two-mirror nonconfocal cavity. The lasers full-width-at-half-maximum linewidth is reduced to 100 Hz, and its instantaneous linewidth to 30 Hz in the Lorentzian fitting. To the best of our knowledge, it is the narrowest linewidth ever achieved with the optical feedback method. The laser phase noise has been significantly reduced by more than 50 dB in the frequency range from 10 Hz to 10 kHz. Our experiment demonstrates the efficient laser linewidth reduction and phase noise suppression by the optical feedback technique.

High-finesse cavity external optical feedback DFB laser with hertz relative linewidth

We report hertz level relative linewidth distributed feedback diode lasers with external optical feedback from a high finesse F-P cavity, and demonstrate the efficient phase noise suppression and laser linewidth reduction of the optical feedback technique. The laser phase noise is dramatically suppressed throughout the measurement frequency range. Especially at the Fourier frequency of 17 kHz, approximately the linewidth of the F-P reference cavity, the laser phase noise is significantly suppressed by more than 92 dB. Above this Fourier frequency, the noise maintains a white phase noise plateau as low as -124.4 dBc/Hz. The lasers FWHM linewidth is reduced from 7 MHz to 4.4 Hz, and its instantaneous linewidth is 220 mHz in the Lorentzian fitting.

Quasi synchronous tuning for grating feedback lasers

A general analytical form of the round trip phase shift in grating feedback diode lasers is proposed. Using the new form, it is obvious that the round trip phase shift can be independent of rotation angle in first order approximation when only one restriction condition is met. We call this the quasi synchronous tuning (QST) condition. In the QST region, a considerably large mode hopping free tuning range can be obtained. An adjustment structure with only one freedom is needed to accurately find and locate the quasi synchronous pivot, which is not strictly confined on the grating surface and its extension. It means that the external cavity diode lasers design can be easier and the laser can be more stable and reliable.

High-finesse F-P cavity external optical feedback narrow linewidth diode laser

We present a narrow linewidth laser by optical feedback from a high-finesse F-P cavity. The cavity transmission feeds back to the laser diode by the external ring path. With a low servo bandwidth system, the feedback phase is compensated for maintaining the optical feedback operation. The linewidth of the optical feedback laser is reduced to 100 Hz, and the laser frequency noise in frequency range of 1 Hz to 10 kHz is suppression over 50 dB. It experimentally demonstrates the excellent characteristics of optical feedback technique.

Design of laser system for absolute gravimeter based on 87Rb atom interferometer

We present a laser system design for an absolute gravimeter based on 87Rb atom interferometer. By skillful design, lasers with 9 different frequencies are based on two diode lasers including tapered amplifier. Two electrical feedback systems are used for laser frequency stabilization and the Raman lasers generation respectively. All other lasers are based on two Raman lasers and realized with frequency shift by acoustic optical modulators. This laser system not only has the compact and simple construction, but meets all requirements for laser power and frequency controlling for the atom interferometer. It has the characteristic of reliability and integrity.