Single-frequency Raman Fiber Amplifier Research Articles

Spectral and RIN properties of single-frequency Raman fiber amplifier co-pumped by ASE source: erratum

Spectral and RIN properties of single-frequency Raman fiber amplifier co-pumped by ASE source: erratum

Spectral and RIN properties of a single-frequency Raman fiber amplifier co-pumped by ASE source.

Spectral and relative intensity noise (RIN) characteristics of a single-frequency Raman fiber amplifier co-pumped by amplified spontaneous emission (ASE) sources are investigated experimentally. Due to the relatively lower intensity noise of ASE sources compared to usual fiber laser pumps, the full width at half maximum (FWHM) linewidth of the signal laser increases negligibly. But there is significant increase in RIN and spectral wings due to the noise transfer at high frequency from the ASE source during the Raman amplification. The deterioration can be suppressed to some extent with ASE of broader linewidth, which has lower intensity noise.

Comprehensive Investigation on the Role of Temporal Property of Pump Laser in a Single-Frequency Raman Fiber Amplifier

Comprehensive Investigation on the Role of Temporal Property of Pump Laser in a Single-Frequency Raman Fiber Amplifier

Intrinsic Mechanism for Spectral Evolution in Single-Frequency Raman Fiber Amplifier

In this paper, the spectral evolution properties in single-frequency Raman fiber amplifier (RFA) based on different pump schemes are analyzed theoretically for the first time based on the gain dynamics. It reveals that the walk-off effect in counter-pumped scheme acts as a natural low-pass filter for single-frequency RFA. When multilongitudinal mode rare-earth-doped fiber laser is used as the pump source for RFA, strong temporal fluctuations of the pump source would lead to spectral broadening in copumped scheme, while single-frequency operation could be maintained in the countered-pumped case because of the natural low-pass filter.

First Demonstration of Co-Pumped Single- Frequency Raman Fiber Amplifier With Spectral-Broadening-Free Property Enabled by Ultra-Low Noise Pumping

Single-frequency Raman fiber amplifier (RFA) has great potential applications in many regimes. Traditionally, counter-pumped manner is widely employed for its spectral linewidth broadening suppressing and maintaining single frequency property. In this paper, we propose the first demonstration of a co-pumped single-frequency RFA without linewidth broadening by applying the fiber laser with stable intensity as the pump source. The pump source with stable intensity is generated by cascaded power amplifying of a low noise, phase-modulated single-frequency seed laser. In this case, experimental results show that single frequency property of the RFA could be effectively maintained in the co-pumped manner. The contrast experiment is given with a conventional multi-longitudinal mode fiber oscillator as a pump source, and the linewidth is gradually broadened along with power scaling.

Investigations of single-frequency Raman fiber amplifiers operating at 1178 nm

We report on core-pumped single-stage and two-stage polarization-maintaining single-frequency Raman fiber amplifiers (RFAs). For a counter-pumped single-stage RFA, commercial-off-the shelf (COTS) single-mode fiber was utilized to generate 10 W of output power at 1178 nm through the application of a two-step thermal gradient in order to suppress SBS. The relatively high output can be explained by the Brillouin gain spectrum (BGS) of the COTS fiber. A pump-probe characterization of the BGS of the fiber provided a Brillouin gain coefficient of 1.2 × 10(-11) m/W with a FWHM of 78 MHz for the gain bandwidth. A fiber cutback study was also conducted to investigate the signal output at SBS threshold as a function of pump power for optimal length. This study revealed a linear dependence, which is in agreement with the theoretical prediction. Furthermore, we present numerical simulations indicating that substantial power scaling can be achieved by seeding at a higher power. Consequently, we constructed a two-stage RFA in order to achieve seed powers at the 1 W level. By utilizing an acoustically tailored fiber possessing a lower Brillouin gain coefficient than the COTS fiber and by seeding at higher powers, 22 W of single-frequency 1178 nm output was obtained from a counter-pumped two-stage RFA. Finally, we show that the single-frequency spectral bandwidth could not be maintained when a similar co-pumped two-stage RFA was utilized.

589 nm laser generation by frequency doubling of a single-frequency Raman fiber amplifier in PPSLT

A high-power single-frequency 1178 nm continuous-wave laser is generated in a two-stage stimulated-Brillouin-scattering-suppressed all-polarization-maintaining Raman fiber amplifier pumped by 1120 nm fiber lasers. A polarization-extinction-ratio of 30 dB is achieved due to the all-polarization-maintaining configuration and the polarization dependence gain of Raman scattering. Single-pass frequency doubling with a homemade periodically poled near-stoichiometric LiTaO(3) crystal (PPSLT) produces an up to 7 W narrow-linewidth laser at 589 nm. The thermally induced dephasing effect is found to be the key issue for improving second-harmonic efficiency.

Investigation on the suppression of stimulated Brillouin scattering in single-frequency Raman fiber amplifiers

High power operation of single-frequency Raman fiber amplifiers (SF-RFAs) is usually limited by the onset of stimulated Brillouin scattering (SBS). In this paper, we present our theoretical investigation on the suppression of SBS in SF-RFAs, based on the intensity equations combining SBS and stimulated Raman scattering (SRS). The effects of increasing the mode area of fiber and utilizing temperature and strain gradients along the fiber on the suppression of SBS are discussed. The simulation results suggest that it is not an advisable method to suppress SBS in SF-RFAs by increasing the mode area. Besides, although tensile strain and temperature gradients can suppress SBS in RFA singly, the conditions are too rigorous to realize. Based on the numerical simulation results, a feasible scheme for the suppression of SBS in RFA is proposed using the temperature gradients together with tensile strain gradients along the fiber length, resulting in an increase of ∼3 times of amplifiers output power.

Analysis and simulation of single-frequency Raman fiber amplifiers

High power operation of single-frequency Raman fiber amplifiers is usually limited by the onset of stimulated Brillouin scattering. A theoretical investigation on single-frequency Raman fiber amplifier limited by stimulated Brillouin scattering is presented in this paper, based on the intensity equations combining stimulated Brillouin scattering and stimulated Raman scattering. A combination of methods is proposed to increase the output power of single-frequency Raman fiber amplifier. These methods include applying a suitable pump scheme according to the fiber length and seed signal power, using short gain fibers, utilizing a multiple-stage scheme and providing suppression of stimulated Brillouin scattering.

Theoretical analysis of single-frequency Raman fiber amplifier system operating at 1178nm

We analyze the scalability of amplifying the output from a single-frequency diode laser operating at 1178 nm through the utilization of a core pumped Raman fiber amplifier. A detailed model that accounts for stimulated Raman scattering (SRS) and stimulated Brillouin scattering (SBS) in relation to the fiber mode field diameter, length, seed power, and available pump power in both co-pumped and counter-pumped configurations is developed. The backward travelling Stokes light is initiated from both spontaneous Brillouin and spontaneous Raman processes. It is found that when fiber length is optimized, the amplifier output scales linearly with available pump power. Although higher amplifier efficiency is obtained with higher seed power, the output power diminishes. In order to mitigate the SBS process for further power scaling, we employ and optimize a multi-step temperature distribution. Finally, we consider the feasibility of generating the D(2a) and D(2b) lines in a sodium guide star beacon from a single Raman amplifier by examining four-wave mixing (FWM).

单频拉曼光纤放大器中受激布里渊散射的抑制

单频拉曼光纤放大器中受激布里渊散射的抑制