Influence of intra-cavity loss on transmission characteristics of fiber Bragg grating Fabry–Perot cavity

A theoretical model of the fiber Bragg grating Fabry–Perot（FBG-FP） transmission spectrum considering loss of FBG and intra-cavity fiber is presented. Several types of FBG-FPs are inscribed experimentally, and their spectra are measured.The results confirm that weak intra-cavity loss is enhanced at the resonance transmission peak, that is, loss of transmission peaks is observably larger than other wavelengths. For FBG-FPs with multi resonance peaks, when the resonance peak wavelength is closer to the Bragg wavelength, the more significant loss effect of resonance transmission peak is exhibited.The measured spectra are fitted with the presented theoretical model. The fitted coefficient of determinations are near 1,which proves the validity of the theoretical model. This study can be applied to measure FBG loss more accurately, without a reference light. It can play an important role in FBG and FBG-FP writing process optimization and application parameter optimization.

An intra-cavity absorption fiber gas sensor based on performanceenhanced techniques

The performance of an erbium-doped fiber ring laser based intra-cavity absorption gassensor was evaluated with performance enhanced techniques. A multi-line wavelength sweep techniqueand a weighted averaging technique were proposed for better gas detection. By selecting appropriatesystem parameters, 6 strong absorption lines near 1 530 nm of C2H2 were obtained with good spectrumresolution in one scanning period. One group with higher absorption coefficients was used for relativelylow gas concentration detection and the other with lower absorption coefficients was used for relativelyhigh gas concentration. Both the groups can be used for medium gas concentration detection. For variousconcentration cases, by choosing proper absorption lines and performing weighted averaging, detectionaccuracy can be obtained over an extended detection range. The minimum detection limit could be verylow after optimization.

Eye-safe intra-cavity diamond cascaded Raman laser with high peak-power and narrow linewidth

The 1.4–1.8μm eye-safe lasers have been widely used in the fields of laser medicine and laser detection and ranging.The diamond Raman lasers are capable of delivering excellent characteristics,such as good beam quality concomitantly with high output power.The intra-cavity diamond Raman lasers have the advantages of compactness and low Raman thresholds compared to the external-cavity Raman lasers.However,to date,the intra-cavity diamond cascaded Raman lasers in the spectral region of the eye-safe laser have an output power of only a few hundred milliwatts.A 1485 nm Nd:YVO_4/diamond intra-cavity cascaded Raman laser is reported in this paper.The mode matching and stability of the cavity were optimally designed by a V-shaped folded cavity,which yielded an average output power of up to 2.2 W at a pulse repetition frequency of 50 kHz with a diode to second-Stokes conversion efficiency of 8.1%.Meanwhile,the pulse width of the second-Stokes laser was drastically reduced from 60 ns of the fundamental laser to 1.1 ns,which resulted in a high peak power of 40 kW.The device also exhibited single longitudinal mode with a narrow spectral width of<0.02 nm.

Line-narrowed electro-optic periodically-poled-lithium-niobate Q-switched laser with intra-cavity optical parametric oscillation using a grazing-incidence grating

We report a line-narrowed electro-optic periodically-poled-lithium-niobate （PPLN） Q-switched laser with intra-cavity optical parametric oscillation using a grazing-incidence grating, producing 8-ns, 5-#J pulses at 10-kHz repetition rate when pumped with a 10-W diode laser at 808 rim. The output wavelength is centered at 1554.3 nm with a 0.03-nm spectral width. Wavelength tuning is achieved by rotating a mirror and changing the crystal temperature.

Output Characteristics of Narrow No-Gain Competition Linewidth Dual-Wavelength Laser at 912 nm and 1064 nm

The output characteristics of a narrow linewidth, no-gain competition, dual-wavelength solid-state laser using an intra-cavity pumped method are reported. This system consists of an intra-cavity pumped Nd:YVO4 laser emitting at 1064 nm, using a 912 nm Nd:GdVO4 laser. A Fabry-Perot etalon is used to compress the linewidth that located at the common cavity of 912 nm and 1064 nm laser. Theoretical analysis and experimental verification were carried out. When the pump power is 32.8 W, the output of 912 nm and 1064 nm theoretical value is 0.036 W and 0.046 W, and the experimental value is 0.017 W and 0.016 W, respectively. The change trend of the theoretical simulated output power value was the same as the actual measured value in the experiment. In addition to this, the experimental measurement shows when the etalon with an angle of 15?, corresponding minimum linewidths were 0.284 nm and 0.627 nm, respectively.