Open Access
Add to BibSonomy
Abstract
We report an efficient and novel method for generating high-peak-power 1.7 µm laser pulses by cascaded optical parametric oscillation (OPO) and stimulated Raman scattering (SRS). The 1064 nm fundamental wave was first converted to 1535 nm by the KTA OPO, and further extended to 1.7 µm by a SRS process. The configuration of OPO + SRS can provide high-intensity pumping light for subsequent Raman conversion, and allows for better wavelength expansibility benefitting from the non-phase-matching requirement of SRS. Two types of Raman conversion using the low-frequency Raman shift in KY(WO4)2 and high-frequency Raman shift in YVO4 were further studied. Up to the 8th-order cascaded KY(WO4)2 Raman laser (KRL) using the high gain 87 cm−1 Raman mode and a YVO4 Raman laser (YRL) using the 890 cm−1 Raman mode emitting at 1.7 µm were realized, respectively. The output wavelengths at 1556, 1577, 1599, 1622, 1646, 1670, 1695, 1720 nm and the output wavelength at 1778 nm were observed in the KRL and YRL, respectively. The maximum total average output powers of 1.26 W and 1.05 W, minimum pulse widths of 8.4 and 24 ns and maximum pulse peak powers of 33.3 kW and 9.4 kW were obtained respectively from the KRL and YRL, enabling the 1.7 µm laser source to have practical applicability in medical imaging, industrial processing, and mid-infrared laser generation.
© 2020 Optical Society of America under the terms of the OSA Open Access Publishing Agreement
1. Introduction
Since the birth of the first ruby laser in 1960s, solid-state lasers have been playing a vital role in exploring new wavelength in the field of laser science and technology. In recent years, developing high-peak-power and cost-effective light sources at 1.7 µm waveband has attracted great attention due to their wide applications in multi-component trace gas detection [1,2], optical coherence tomography [3–6], laser therapy [7–9], mid-infrared laser generation [10–12], etc. Lots of erbium (Er)- and holmium (Ho)-doped crystals or ceramics have been reported as gain media to generate 1.6 µm and 1.8-2 µm emissions [13–20], respectively. Nevertheless, common gain media efficiently emitting at 1.7 µm is rarely reported. Adopting special ions doped fibers as optical gain medium can produce gain at 1.7 µm waveband, such as bismuth-doped fibers (BDFs) [21,22] and thulium-doped fibers (TDFs) [23–25]. However, this kind of 1.7 µm fiber laser usually faced the problems of weak gain spectral region of active ions, unconventional pumping wavelength and low output pulse energy.
Another technical solution for developing 1.7 µm solid-state lasers is using nonlinear optical frequency conversions (NOFCs). OPO and SRS are two kinds of technical schemes to realize the extension of conventional wavelengths to longer wavelengths. OPO is a second-order nonlinear process whose performance depends on the constraints of matching conditions. Raman conversion does not require birefringent- or quasi-phase matching, but need high intensity pumping light for efficient conversion due to the third-order nonlinearity of SRS. In order to further developing a flexible and reliable 1.7 µm laser source to solve the problems caused by the single OPO or SRS technique, cascaded nonlinear optical frequency conversions (CNOFCs) involving the OPO and SRS process are proposed. In 2011, F. Bai et al. employed a SrWO4 Raman laser to pump an intracavity noncritically phase-matched (NCPM) KTiOPO4 (KTP) OPO to generate 1.8 µm emissions with a maximum average power output of 485 mW [26]. In 2018, H. Y. Zhu et al. demonstrated an intracavity KTiOAsO4 (KTA) OPO pumped by a Nd:YVO4 self-Raman laser at 1176 nm to generate 1742 nm laser pulses [27]. In order to implement the NCPM OPO in these CNOFCs-based lasers described by the configuration of OPO pumped by a Raman laser (SRS + OPO), the emission wavelength from the front Raman conversion must satisfy the phase matching requirement of the subsequent OPO. Due to the restriction of the later OPO, single-wavelength was always operated in this configuration of SRS + OPO. Therefore, it is attractive to explore new-type CNOFCs-based laser with better designability and compatibility. Recently, our group proposed a CNOFC scheme utilizing an OPO to intracavity pump the Raman conversion, forming the configuration of OPO + SRS [28]. Compared with the conventional configuration of SRS + OPO, the CNOFC of OPO + SRS have the following comparable advantages. Firstly, the front OPO conversion can be operated with the noncritical phase matching to obtain the higher optical conversion efficiency without special consideration on the signal wavelength. Secondly, OPO as a pre-process can provide high-intensity pumping light for subsequent multi-order Raman conversions due to the OPO cavity dumping [29]. Thirdly, the rear-mounted SRS will offer greater wavelength diversity by choosing different Raman shifts of Raman crystals. In addition, the design of the CNOFC of OPO + SRS can generate higher-peak-power 1.7 µm pulses compared to the Tm/Ho-codoped or Bi-doped fiber pulsed laser [22,25]. It can also use the commercially available bulk nonlinear crystals with high cost effectiveness, with no need for complex micro-structured optical devices.
In this paper, we experimentally demonstrated a novel design of OPO + SRS for generating high-peak-power 1.7 µm laser pulses. The 1064 nm fundamental wave was first converted to 1535 nm by the KTA OPO, and further extended to 1.7 µm by a SRS process. Two types of Raman conversion using the low-frequency Raman shifts in KY(WO4)2 (KYW) and high-frequency Raman shifts in YVO4 were further studied. Up to 8th-order KYW Raman laser (KRL) using the high gain 87 cm−1 Raman mode and a 1st-order YVO4 Raman laser (YRL) using 890 cm−1 Raman mode intracavity pumped by a 1535 nm KTA OPO were demonstrated respectively. The KRL operated at multiple wavelengths, with emissions at 1556, 1577, 1599, 1622, 1646, 1670, 1695, and 1720 nm. The YRL emitted at single wavelength of 1778 nm. The pulse compression effect was easier to obtain a narrower pulse width and a higher peak-power due to the OPO cavity dumping and the pulse shortening of SRS. The maximum total average output powers of 1.26 W and 1.05 W, minimum pulse widths of 8.4 and 24 ns, and maximum pulse peak powers of 33.3 kW and 9.4 kW were obtained respectively from the KRL and YRL, filling the gap of generating the high-peak-power 1.7 µm laser source and enabling the laser source to have practical applicability in medical imaging, industrial processing and mid-infrared laser generation.
2. Design considerations and experiments setup
The choice of nonlinear crystals is an important consideration for designing the CNOFC of OPO + SRS. For the selection of the OPO medium, as the isomorphs of KTP, KTA crystal not only has a large χ(2)-nonlinearity but also high transparency range (0.35-5.3 µm) and high optical damage threshold. The x-cut KTA crystal was used as OPO crystal to generate the high-intensity lights at 1535 nm pumped by the well-developed 1064 nm [30]. For the choice of Raman crystal, two types of Raman crystals with low- and high-frequency Raman shifts were utilized to obtain the 1.7 µm pulses, respectively. KYW crystal, a member of double metal tungstates, has shown great potential in efficient Raman conversions due to its relative high thermal conductivity, moderate Raman gain, high optical damage threshold and robust mechanical properties [31,32]. The previous works on KYW-based Raman lasers mainly focused on the well-known Raman shift of 765 cm−1 and 905 cm−1. However, the stronger 87 cm−1 mode of KYW has a higher Raman gain coefficient of 9.2 cm/GW than that of 3.6 cm/GW for 905 cm−1 and 2.5 cm/GW for 225 cm−1 mode [32–34]. Another Raman crystal is YVO4 crystal that has large χ(3)-nonlinearity to achieve SRS conversions as well [35–36]. The 890 cm−1 mode of YVO4 with the Raman gain coefficient is no less than 4.5 cm/GW due to the fact that the YVO4 crystal belongs to the totally symmetric (stretching) optical vibration modes of their tetrahedral VO43− ionic group [37–39].
The diagrammatic sketch for the experimental setup of the cascaded KRL and YRL intracavity pumped by a KTA OPO is displayed in Fig. 1. As shown in Fig. 1(a), the KRL cavity was made up of an input mirror RM, an acoustic optic (AO) Q-switch, a Nd:YAG module, an intermediate mirror IM, a KTA crystal, a KYW crystal and an output coupler OC. The length of the cavity was 215 mm. RM was a plano-concave mirror with 1000 mm radius of curvature, which was high-reflection coated at 1064 nm (R > 99.8%) on the concave surface. The used AO Q-switch had antireflection coatings at 1064 nm on both light-passing surfaces and was driven at a center frequency of 24 MHz with a radio-frequency power of 50 W. The Nd:YAG module had a water-cooled Nd:YAG rod with a dimension of 3 mm in diameter and 65 mm in length that was side-pumped by radial laser-diode (LD) arrays. The plano-plane IM was high-reflection coated at 1520-1750 nm (R > 99.9%), high-transmission coated at 1064 nm on one surface, and anti-reflection coated at 1064 nm on the other surface. Both the 4 mm × 4 mm × 30 mm KTA and 5 mm × 5 mm × 10 mm KYW crystal were wrapped with indium foil and mounted in copper block cooled by water at a temperature of 20°C. Both the two crystals were high-transmission coated at 1064 and 1500-1700 nm. Figure 2 shows the transmittance of the IM and OC used in the KRL in the wavelength range of 1500-1800 nm. The transmittances of plano-plane OC at the wavelengths of 1064, 1535, 1556, 1577, 1599, 1622, 1646, 1670, 1695, 1720 and 1778 nm were 0.01%, 0.01%, 0.01%, 0.01%, 0.01%, 0.07%, 0.04%, 0.27%, 2.3%, 40.6%, and 58.2% respectively. Similarly, as shown in Fig. 1(b), the KYW crystal was only replaced by the 5 mm × 5 mm × 10 mm YVO4 crystal with high-transmission coated at 1064 and 1500-1700 nm mounted in copper block cooled by water at a temperature of 24°C. Therefore, the 1064 nm resonance could be established between RM and OC, while KTA OPO and multi-order KYW SRS or YVO4 SRS shared the same resonator comprised of IM and OC.
Fig. 1. The diagrammatic sketch for the experimental setup of the cascaded KYW and YVO4 Raman lasers intracavity pumped by a KTA OPO. (a) corresponds to KRL; (b) corresponds to YRL.
In the operation of the KRL, the 1064 nm was first set as the starting wavelength to pump the NCPM KTA-OPO to generate the signal wave at 1535 nm. The KTA OPO as an intracavity excitation source could provide high-intensity pumping light for subsequent Raman conversion. Then under the Np[NgNg]Np Raman configuration, the KYW using the 87 cm−1 Raman shift converted the OPO signals to multi-order Stokes lights due to the fact that the output coupler has a high reflectivity at the low-order Stokes wavelengths. In the same way, the high-peak-power 1st-order Stokes light at 1778 nm was achieved by the OPO signals at 1535 nm in YRL using the 890 cm−1 Raman shift in YVO4 crystal.
3. Experimental results
3.1 Multi-order cascaded Raman conversion with low-frequency Raman shift in KYW
The output spectrums of the cascaded KRL were first measured with a spectrometer (AQ6376, Yokogawa), with the results shown in Fig. 3. In addition to the weak KTA OPO signal at 1535 nm, multiple emission lines at 1556, 1577, 1599, 1622, 1646, 1670, 1695, and 1720 nm were observed, respectively, corresponding to the 1st- to 8th-order Stokes waves induced by the 87 cm−1 Raman shift in KYW. As shown in Fig. 2, the IM and OC were high-reflection coated at 1550-1680 nm, enabling a good resonance condition for the multi-order 87 cm−1-based Raman conversion. Then the higher order of 7th- and 8th-order Stokes at 1695 and 1720 nm always dominated the output spectrum with the LD pump power increasing. It should be noted that 1738 and 1781 nm, corresponding to the first Stokes respectively via the 765 cm−1 and 905 cm−1 Raman shift in KYW under 1535 nm pumping, were not observed. This is due to the higher transmittances of 66.4% and 62.2% of OC at the two wavelengths, introducing higher SRS threshold for the 765 cm−1 and 905 cm−1 Raman modes. These results definitely indicate successful realization of the design of CNOFC of OPO + SRS using the low-frequency Raman shift.
Figure 4 shows the dependence of average output power and pulse width on the LD pump power achieved at an optimized AO repetition rate of 4.5 kHz in the KRL. The pulse width was recorded using a 1 GHz digital oscilloscope (DSO-S104A, Keysight) and a photodetector (DET10D2, Thorlabs). Due to the approximately 20 nm wavelength separation between the multiple wavelengths, it was hard for us to accurately measure the average output power at each single wavelength. So the average output power shown in Fig. 4 was the total average output power. The 808 nm LD pump power thresholds for the 1st- and 8th-order Raman conversions were 135 W and 150 W, respectively. As the LD pump power increased, the average output power increased but the pulse width was decreased sharply. A maximum average output power of 1.26 W and a minimum pulse width of 8.4 ns were obtained at an 808 nm LD pump power of 220 W and a pulse repetition rate (PRF) of 4.5 kHz. The poor spatial mode-matching between the 808 nm and 1064 nm beams in the LD side-pump Nd:YAG module can account for the low optical conversion efficiency from 808 nm pump to Raman light [29].
Fig. 4. The dependence of average output power and pulse width on the LD pump power. Inset: the dependences of the output powers on the LD pump power for the 1064 nm Nd:YAG laser in the CW and Q-switched mode.
Under the OPO cavity dumping and pulse shortening effect of multiple SRS conversion [40], the strong pulse narrowing was observed. The pulse width was decreased with the LD pump power increasing and reached a minimum pulse width of 8.4 ns. Figures 5(a) and 5(b) display the multi-wavelengths form with a pulse width of 8.4 ns and corresponding pulse train with a repetition rate of 4.5 kHz with the average output power of the KRL reaching its maximum, and the corresponding peak power and pulse energy were calculated to be 33.3 kW and 0.28 mJ, respectively. This novel design of CNOFC of OPO + SRS was more practical value in the peak power and wavelength diversity than the CNOFC of SRS + OPO reported in Refs. [26] and [27].
Fig. 5. The typical single pulse and corresponding pulse trains of the KRL and YRL. (a) and (b) correspond to the multi-wavelengths of KRL. (c) and (d) correspond to the YRL.
3.2 First-order Raman conversion with high-frequency Raman shift in YVO4
As shown in Fig. 3, the output spectrums of the YRL were also obtained with a spectrometer (AQ6376, Yokogawa). Except for the weak KTA OPO signal at 1535 nm, the 1st-order Stokes wave at 1778 nm induced by the 890 cm−1 Raman shift in YVO4 was only observed and the signal wavelength was determined to be 1778 nm.
Figure 6 shows the dependence of average output power and pulse width on the LD pump power achieved at an optimized AO repetition rate of 4.5 kHz in the YRL. The 808 nm LD pump power thresholds for the 1st-order Raman conversion was 155 W. When the LD pump power was up to 215 W, a maximum average output power of 1.05 W and a minimum pulse width of 24 ns were obtained with a pulse repetition rate (PRF) of 4.5 kHz. As shown in Figs. 5(c) and 5(d), the wave form with a pulse width of 24 ns and corresponding pulse train with a repetition rate of 4.5 kHz were presented when the average output power of the YRL was up to the maximum. The corresponding peak power of 9.4 kW and pulse energy of 0.23 mJ was obtained by calculated, respectively.
Fig. 6. The dependence of average output power and pulse width on the LD pump power. Inset: the dependences of the output powers on the LD pump power for the 1064 nm Nd:YAG laser in the CW and Q-switched mode.
4. Conclusions
We have demonstrated a novel design of CNOFC of OPO + SRS for generating high-peak-power 1.7 µm laser pulses. Two types of Raman conversion using the low-frequency Raman shifts in KYW and high-frequency Raman shifts in YVO4 have been realized. The output wavelengths at 1556, 1577, 1599, 1622, 1646, 1670, 1695, 1720 nm were observed in the KRL which used the high gain 87 cm−1 Raman mode in KYW. The output wavelength at 1778 nm was detected in the YRL, using the 890 cm−1 Raman shift in YVO4. Under the dual-pulse-compression effect by the cascaded χ(2)- and χ(3)-nonlinearity, maximum pulse peak powers of 33.3 kW and 9.4 kW were obtained respectively from the KRL and YRL. These results represent that high-peak-power 1.7 µm laser source has practical applicability in terahertz radiation and mid-infrared laser generation. In addition, the new configuration of OPO + SRS by cascaded second- and third-order nonlinearity may open a new door for developing high-peak-power, high-beam-quality Raman lasers at longer wavelength.
Funding
National Natural Science Foundation of China (61605068, 61875077, 61911530131, U1730119); Applied Basic Research Programs of Xuzhou (KC17085); Natural Science Foundation of the Jiangsu Higher Education Institutions of China (18KJA510001); Priority Academic Program Development of Jiangsu Higher Education Institutions.
Disclosures
The authors declare no conflicts of interest.
References
1. H. Barry, L. Corner, and G. Hancock, “Cross sections in the 2ν5 band of formaldehyde studied by cavity enhanced absorption spectroscopy near 1.76 µm,” Phys. Chem. Chem. Phys. 4(3), 445–450 (2002). [CrossRef]
2. P. Chambers, E. Austin, and J. P. Dakin, “Theoretical analysis of a methane gas detection system, using the complementary source modulation method of correlation spectroscopy,” Meas. Sci. Technol. 15(8), 1629–1636 (2004). [CrossRef]
3. M. Tanaka, M. Hirano, K. Murashima, H. Obi, R. Yamaguchi, and T. Hasegawa, “1.7-µm spectroscopic spectral domain optical coherence tomography for imaging lipid distribution within blood vessel,” Opt. Express 23(5), 6645–6655 (2015). [CrossRef]
4. S. P. Chong, C. W. Merkle, and D. F. Cooke, “Noninvasive, in vivo imaging of subcortical mouse brain regions with 1.7 µm optical coherence tomography,” Opt. Lett. 40(21), 4911 (2015). [CrossRef]
5. Y. Li, N. T. Sudol, Y. Miao, J. C. Jing, J. Zhu, F. Lane, and Z. Chen, “1.7 micron optical coherence tomography for vaginal tissue characterization in vivo,” Lasers Surg. Med. 51(2), 120–126 (2019). [CrossRef]
6. E. J. Jung, J. H. Lee, B. S. Rho, M. J. Kim, and C. S. Kim, “Spectrally sampled OTC imaging based on 1.7 µm continuous-wave supercontinuum source,” IEEE J. Sel. Top. Quantum Electron. 18(3), 1200–1208 (2012). [CrossRef]
7. N. M. Htun, Y. C. Chen, and B. Lim, “Near-infrared autofluorescence induced by intraplaque hemorrhage and heme degradation as marker for high-risk atherosclerotic plaques,” Nat. Commun. 8(1), 75 (2017). [CrossRef]
8. D. Chai, G. Chaudhary, and M. S. Eric Mikula, “In vivo femtosecond laser subsurface scleral treatment in rabbit eyes,” Lasers Surg. Med. 42(7), 647–651 (2010). [CrossRef]
9. M. Muniyappa, “Glycosylation as a marker for inflammatory arthritis,” Cancer Biomarkers 14(1), 17–28 (2014). [CrossRef]
10. R. S. Quimby, L. B. Shaw, and J. S. Sanghera, “Modeling of cascade lasing in Dy: chalcogenide glass fiber laser with efficient output at 4.5 µm,” IEEE Photonics Technol. Lett. 20(2), 123–125 (2008). [CrossRef]
11. H. Jelínková, M. E. Doroshenko, and M. Jelínek, “Dysprosium-doped PbGa2S4 laser generating at 4.3 µm directly pumped by 1.7 µm laser diode,” Opt. Lett. 38(16), 3040 (2013). [CrossRef]
12. D. Novoa, J. C. Travers, and M. Cassataro, “Generation of broadband mid-IR and UV light in gas-filled single-ring hollow-core PCF,” Opt. Express 25(7), 7637 (2017). [CrossRef]
13. L. Galecki, M. Eichhorn, and W. Zendzian, “Pulsed 1.645 µm Er3+:YAG laser with increased average output power and diffraction limited beam quality,” Laser Phys. Lett. 10(10), 105813 (2013). [CrossRef]
14. C. Larat, M. Schwarz, and E. Lallier, “120mJ Q-switched Er:YAG laser at 1645 nm,” Opt. Express 22(5), 4861–4866 (2014). [CrossRef]
15. A. Z. Li, M. Zhang, X. Wang, S. B. Wang, B. G. Guo, and A. Li, “Directly Pumped Ho3+-Doped Microspheres Lasing at 2 µm,” IEEE Photonics Technol. Lett. 31(16), 1366–1368 (2019). [CrossRef]
16. H. Huang, D. Shen, and J. Zhang, “Q-switched mode locking of a fiber laser resonantly pumped Er:YAG ceramic laser at 1645 nm using graphene as saturable absorber,” J. Nonlinear Opt. Phys. Mater. 24(01), 1550001 (2015). [CrossRef]
17. S. Rostami, R. A. Alexander, V. Azzurra, and M. Sheik-Bahae, “Observation of optical refrigeration in a holmium-doped crystal,” Photonics Res. 7(4), 445–451 (2019). [CrossRef]
18. P. Fjodorow, O. Hellmig, and V. M. Baev, “A broadband Tm/Ho-doped fiber laser tunable from 1.8 to 2.09 µm for intracavity absorption spectroscopy,” Appl. Phys. B 124(4), 62 (2018). [CrossRef]
19. A. V. Kir’yanov, Y. O. Barmenkov, I. L. Villegas-Garcia, J. L. Cruz, and M. V. Andres, “Highly Efficient Holmium-Doped All-Fiber 2.07-µm Laser Pumped by Ytterbium-Doped Fiber Laser at 1.13 µm,” IEEE J. Sel. Top. Quantum Electron. 24(5), 1–8 (2018). [CrossRef]
20. A. Lin, J. He, H. Zhan, A. D. Zhang, and A. X. Lin, “Study on 2.0 µm fluorescence of Ho-doped water-free fluorotellurite glasses,” Opt. Mater. 35(22), 2573–2576 (2013). [CrossRef]
21. S. V. Firstov, S. V. Alyshev, K. E. Riumkin, M. A. Melkumov, O. I. Medvedkov, and E. M. Dianov, “Watt-level, continuous-wave bismuth-doped all-fiber laser operating at 1.7 µm,” Opt. Lett. 40(18), 4360–4363 (2015). [CrossRef]
22. L. P. Wang, J. K. Cao, and Y. Lu, “In situ instant generation of an ultrabroadband near-infrared emission center in bismuth-doped borosilicate glasses via a femtosecond laser,” Photonics Res. 7(3), 300–310 (2019). [CrossRef]
23. M. Sabra, B. Leconte, R. Dauliat, D. Darwich, T. Tiess, A. Schwuchow, R. Jamier, G. Humbert, and K. Wondraczek, “Widely tunable Q-switched dual-wavelength synchronous-pulsed Tm-doped fiber laser emitting in the 2 µm region,” Opt. Lett. 44(19), 4690–4693 (2019). [CrossRef]
24. J. M. O. Daniel, N. Simakov, and M. Tokurakawa, “Ultra-short wavelength operation of a thulium fibre laser in the 1660–1750nm wavelength band,” Opt. Express 23(14), 18269–18276 (2015). [CrossRef]
25. T. J. Du, Q. J. Ruan, R. H. Yang, and Z. Q. Luo, “1.7 µm Tm/Ho-codoped all-fiber pulsed laser based on intermode-beating modulation technique,” J. Lightwave Technol. 36(20), 4894–4899 (2018). [CrossRef]
26. F. Bai, Q. P. Wang, Z. J. Liu, X. Y. Zhang, W. J. Sun, X. B. Wan, P. Li, G. F. Jin, and H. J. Zhang, “Efficient 1.8 µm KTiOPO4 optical parametric oscillator pumped within an Nd:YAG/SrWO4 Raman laser,” Opt. Lett. 36(6), 813–815 (2011). [CrossRef]
27. H. Y. Zhu, J. H. Guo, Y. M. Duan, J. Zhang, Y. C. Zhang, C. W. Xu, H. Y. Wang, and D. Y. Fan, “Efficient 1.7 µm light source based on KTA-OPO derived by Nd:YVO4 self-Raman laser,” Opt. Lett. 43(2), 345–348 (2018). [CrossRef]
28. H. W. Chen, H. T. Huang, S. Q. Wang, and D. Y. Shen, “A high-peak-power orthogonally-polarized multi-wavelength laser at 1.6-1.7 µm based on the cascaded nonlinear optical frequency conversion,” Opt. Express 27(17), 24857–24865 (2019). [CrossRef]
29. H. Huang, H. Wang, and S. Wang, “Designable cascaded nonlinear optical frequency conversion integrating multiple nonlinear interactions in two KTiOAsO4 crystals,” Opt. Express 26(2), 642 (2018). [CrossRef]
30. Y. M. Duan, H. Z. Zhu, C. W. Xu, X. K. Ruan, G. H. Cui, Y. J. Zhang, D. Y. Tang, and D. Y. Fan, “Compact self-cascaded KTA-OPO for 2.6 µm laser generation,” Opt. Express 24(23), 26529–26535 (2016). [CrossRef]
31. S. Grabtchikov, A. N. Kuzmin, V. A. Lisinetskii, V. A. Orlovich, A. A. Demidovich, M. B. Danailov, H. J. Eichler, A. Bednarkiewicz, W. Strek, and A. N. Titov, “Laser operation and Raman self-frequency conversion in Yb:KYW microchip laser,” Appl. Phys. B 75(6-7), 795–797 (2002). [CrossRef]
32. S. Soumya, R. J. Williams, O. Lux, O. Kitzler, A. McKay, H. Jasbeer, and P. M. Richard, “High-gain 87 cm−1 Raman line of KYW and its impact on continuous-wave Raman laser operation,” Opt. Express 24(19), 21463–21473 (2016). [CrossRef]
33. A. Kaminskii, A. Konstantinova, V. Orekhova, A. Butashin, R. Klevtsova, and A. Pavlyuk, “Optical and nonlinear laser properties of the χ(3)-active monoclinic α-KY(WO4)2 crystals,” Crystallogr. Rep. 46(4), 665–672 (2001). [CrossRef]
34. L. Macalik, J. Hanuza, and A. A. Kaminskii, “Polarized Raman spectra of the oriented NaY(WO4)2 and KY(WO4)2 single crystals,” J. Mol. Struct. 555(1-3), 289–297 (2000). [CrossRef]
35. W. Jiang, Z. Li, and S. Zhu, “YVO4 Raman laser pumped by a passively Q-switched Yb:YAG laser,” Opt. Express 25(13), 14033 (2017). [CrossRef]
36. Y. F. Chen, Y. Y. Pan, Y. C. Liu, H. P. Cheng, C. H. Tsou, and H. C. Liang, “Efficient high-power continuous-wave lasers at green-lime-yellow wavelengths by using a Nd:YVO4 self-Raman crystal,” Opt. Express 27(3), 2029–2035 (2019). [CrossRef]
37. A. Kaminskii, H. Eichler, H. Rhee, and K. Ueda, “New manifestations of nonlinear χ(3) -laser properties in tetragonal YVO4 crystal: many-phonon SRS, cascaded self-frequency “tripling”, and self-sum-frequency generation in blue spectral range with the involving of Stokes components under one-micron picosecond pumping,” Laser Phys. Lett. 5(11), 804–811 (2008). [CrossRef]
38. A. A. Kaminskii, K. I. Ueda, and H. J. Eichler, “Tetragonal vanadates YVO4 and GdVO4 - new efficient χ(3)-materials for Raman lasers,” Opt. Commun. 194(1-3), 201–206 (2001). [CrossRef]
39. X. Wang, X. Wang, and J. Dong, “Multi-wavelength, sub-nanosecond Yb:YAG/Cr4+:YAG/YVO4 passively Q-switched Raman microchip laser,” IEEE J. Sel. Top. Quant. 24(5), 1–8 (2018). [CrossRef]
40. R. Frey, A. de Martino, and F. Pradère, “High-efficiency pulse compression with intracavity Raman oscillators,” Opt. Lett. 8(8), 437–439 (1983). [CrossRef]
