Guofeng Xin

Tunable External Cavity Diode Laser With a PLZT Electrooptic Ceramic Deflector

A stable tunable diode laser which uses an electrooptic deflector incorporated into a Littrow-type external cavity as a wavelength tunable element is proposed and demonstrated. The deflector is fabricated by lead lanthanum zirconate titanate (PLZT) electrooptic ceramic with high quadratic electrooptic effect. Two half-wave plates and a large angle triangular electrode of PLZT electrooptic ceramic are designed to acquire a high frequency-voltage tuning ratio. By adjusting the voltage applied to the deflector, a large single-mode tuning range of 420 GHz (including mode hops) and a frequency-voltage tuning ratio of 840 GHz/kV have been achieved at 780.5 nm.

Narrow linewidth hybrid integrated external cavity diode laser for precision applications

A butterfly-packaged narrow-linewidth hybrid integrated external cavity diode laser module based on the polarization maintaining fiber Bragg grating is reported. The module emits at the wavelength of 1550 nm and provides 21 GHz of continuous tunability. It produces ≥ 20 mW of polarization maintaining fiber-coupled output power with intrinsic Lorentz linewidth ≤ 3 kHz and RIN ≤140 dB/√Hz@100 kHz. To qualify the reliability of the laser module under harsh environmental conditions, random vibration test and high-low temperature cycling test are carried out, and no degradation of the power current characteristic is observed.

Mode-hop-free electro-optically tuned external-cavity diode laser with a volume Bragg grating

A novel electro-optically tuned external-cavity diode laser with volume Bragg grating (VBG) is proposed and demonstrated experimentally. A piece of high electro-optic coefficient Lead Lanthanum Zirconate Titanate (PLZT) transparent ceramic is inserted into the external cavity to act as a refractive index tunable component to change the cavity length. By adjusting the voltage applied to the PLZT, a single mode tuning range of 2.5G without mode hoping is achieved. The laser wavelength is around 810.0nm with the line-width of 19MHz and the SMSR of 37dB.

Design of a mode-hop-free tunable external cavity diode laser with a PLZT electro-optic ceramic deflector

A stable tunable external cavity diode laser (ECDL) which uses an intracavity electro-optic deflector incorporated into a Littrow-type external cavity as a wavelength tunable element is proposed. The deflector comprises an antireflection-coated rectangle Lead Lanthanum Zirconate Titanate (PLZT) electro-optic ceramic with a pair of parallel trapezoidal electrodes on the up and down surfaces, which can simultaneously change the cavity length and the beam-grating angle to achieve mode-hop-free tuning. The theory for mode-hop-free tuning will be presented in this paper, and the model calculations predict that the laser can be tuned continuously by as much as 110GHz. This new approach is simple in structure with no mechanical moving parts and has potential configuration of compact grating-stabilized ECDL.

Improve Beam Quality of High-power Laser Diode Array Stacks by External-cavity Technique

Because of its own structures limitation, the beam divergence angle of the semiconductor laser is very large. In the fastaxis direction, the beam plays good quality and can be collimated less than 1° by using cylindrical micro-lens. However, in the slow-axis direction, the beam quality is too poor to be collimated to a small pattern. This could limit its application in the fields which need high beam quality. For high-power laser diode array (LDA), external-cavity technique can make all the emitters working in the same wavelength, and can improve their beam quality. In this paper, direct feedback method was employed to achieve cross-injection between 25 emitters of a LD bar by using a stripe mirror. At a certain cavity length, after the reflection of the external-cavity mirrors reflective stripe, the beam with large slow-axis divergence angle will feedback to the spacer region between the emitters and lose its energy, or would exactly feedback to the neighbor emitter. Simultaneously, the beam with small divergence angle would output from the transparent stripe of the external-cavity mirror. The slow-axis divergence of the stacks with two bars was suppressed from 6°to 2°by using this technique.