Efficient operation near the quantum limit in external cavity diamond Raman laser

Abstract

We realize efficient operation of the first Stokes (1240.3 nm) and the second Stokes (1485.8 nm) in external cavity diamond Raman lasers (DRLs) through efficient cavity coupling management and study their output performance. Firstly, an output pulse energy of 0.26 mJ at the first Stokes is generated and the slope efficiency is 84.3%, which closely approaches the quantum limit of 85.8%. Secondly, an output pulse energy of 0.26 mJ at the first Stokes and 0.18 mJ at the second are generated simultaneously. The total Raman output pulse energy is 0.44 mJ with a slope efficiency of 73.0%. To our knowledge, this is the highest slope efficiency in dual-wavelength external cavity DRLs. At the maximum pump level, by managing the cavity coupling, the energy ratio of the second Stokes to the first can be changed from 0.69 to 1.92. Highly efficient operation in external cavity DRLs is very important in practical applications, such as remote sensing, scanning lidar and laser range finding.

A review of ns-pulsed Raman lasers based on diamond crystal

“…The slope efficiency defined as the slope of the curve obtained by plotting the laser output power versus the pump power is a crucial index to evaluate the Raman laser performance, since it is determined by comprehensive factors of the resonator, including bulk absorption loss, Raman quantum defect, the output coupling of the laser resonator and so on. Due to the commercialization of high-quality single-crystal diamond, DRLs have shown near quantum-limited high slope efficiency [24,25].…”

“…The most effective way is to optimize the input and output coupler coatings. Hence, Yao Wang et al from China Academy of Engineering Physics, studied the relationship between cavity coupling and their output characteristics in 2020 [25]. The experimental setup is similar to the reference [24] shown in Figure 1.…”

“…The experimental setup in [25]. HWP, half-wave plate; ISO, optical isolator; TM, turning mirror; FL, focus lens; IM, input mirror; OC, output coupler; LF, long-pass filter.…”

“…With these extraordinary characteristics, a considerable amount of literature has been published on diamond Raman lasers (DRLs) in the last decade. The remarkable achievements of DRLs have been incorporated into various Raman laser formats, including deep UV [17], visible [18][19][20][21][22][23], NIR [24][25][26][27][28][29][30] and MIR [31] wavelengths in continuous wave (CW) [32], quasi-CW (QCW) [28][29][30] and pulsed [18,22,[24][25][26][33][34][35][36][37] regimes. For the ns-pulsed DRL, maximum pulse energy of 9 mJ at 1.240 μm with pulse width of 8 ns and conversion efficiency of 24% has been reported by Robert J. Williams at Macquarie University [38].…”

Numerical Simulation of Long-Wave Infrared Generation Using an External Cavity Diamond Raman Laser

“…Theoretically, as the dephasing time of the vibrational excitation is of order of 10 ps for crystals [20], the Stokes pulse width is close to that of the pump when the overall gain of the oscillator is large enough for a crystalline Raman laser pumped by tens of nanoseconds pulse (or longer). However, restricted by Raman gain coefficient, crystal length, intracavity diffraction loss, as well as resonator structure, Stokes beam cannot oscillate and output in a very short time, which leads to an obvious pulse compression effect during Raman conversion [21,22]. In view of this situation, we simply analyze the changes of pump and Stokes intensity in time domain in a Raman oscillator.…”