- Email: [email protected]
CW mode-locked self-Raman 1.17 μm Nd: GdVO4 laser with a novel long cavity
Optics & Laser Technology 58 (2014) 39–42
Contents lists available at ScienceDirect
Optics & Laser Technology journal homepage: www.elsevier.com/locate/optlastec
CW mode-locked self-Raman 1.17 μm Nd: GdVO4 laser with a novel long cavity Z.H. Li a,b, J.Y. Peng a,b,n, Y. Zheng a,b a b
Insitute of Laser, School of Science, Beijing Jiaotong University, Beijing 100044, China Key Laboratory of Luminescence and Optical Information, Ministry of Education, Beijing 100044, China
art ic l e i nf o
a b s t r a c t
Article history: Received 18 September 2013 Received in revised form 28 October 2013 Accepted 31 October 2013 Available online 16 November 2013
In this paper we report on a mode-locked self-Raman 1.17 μm Nd:GdVO4 laser. We successfully achieved stable CW mode-locked pulse in a diode-pumped self-Raman Nd:GdVO4 laser with a novel design of cavity included a dichroic mirror used in a special way. With an incident pump power of 10 W, the average output powers was up to 103 mW at a repetition rate of 145 MHz. & 2013 Elsevier Ltd. All rights reserved.
Keywords: Self-Raman Nd:GdVO4 Mode-locked
1. Introduction No matter how new laser materials are continuously developed, only a few wavelengths can be generated directly in solid state laser materials. In recent years frequency shifting of laser pulses by stimulated Stokes Raman scattering in laser crystals has attracted many people's attention, which become a promising method to generate laser efficiently at many new wavelengths. Q-switched and CW (continuous wave) self-Raman lasers based on Nd-doped and Yb-doped laser crystals have been demonstrated, which provide the first Stokes line in the near infrared region between 1100 and 1200 nm [1–6]. With the frequency doubling, these lasers generate radiation at wavelengths in the yellow–orange spectral region, for the use of sodium guide star laser, ecological monitoring techniques, etc. However, few mode-locked self-Raman lasers were reported. The CW mode-locked laser can be used in many fields, such as laser machining, light detection and ranging, nonlinear optical transformation, wind scanner, geo-seismic sensing for oil & gas, etc. In 2006, a passively Q-switched mode-locked Nd:YVO4 self-Raman laser with SESAM was demonstrated by Weitz [7]. In 2012, a Q-switched and mode-locked Nd3 þ :YVO4 self-Raman laser with Cr4 þ :YAG was also achieved by our research group [8]. In 2008, a passively CW mode-locked Nd:YVO4 self-Raman laser was reported by Weitz [9]. As the huge three-order nonlinearity of
n Corresponding author at: Beijing Jiaotong University, Insitute of Laser, School of Science, No. 3 Shang Yuan Cun, Hai Dian Dist, Beijing 100044, China. Tel.: þ 860 105 168 4716. E-mail addresses: [email protected], [email protected] (J.Y. Peng).
0030-3992/$ - see front matter & 2013 Elsevier Ltd. All rights reserved. http://dx.doi.org/10.1016/j.optlastec.2013.10.035
Nd:GdVO4, it is not only relative to the Kerr-lens mode locking [10], but also related to the stimulated Stokes Raman scattering. In this paper, we experimentally demonstrated a CW mode-locked selfRaman Nd:GdVO4 laser with a novel z-shaped cavity included a dichroic mirror used in a different way. The dichroic mirror was used as both the output coupler and splitting mirror. And a SESAM was utilized as the CW mode locked element. As an empirical value for the energy fluence required for stable mode-locked operation is about three to five times the saturation fluence [11], an efficient laser cavity was designed by using the ABCD matrix. We successfully observed stable CW mode-locked self-Raman pulse train in this laser. Moreover, we observed both Q-switched mode-locked and CW mode-locked pulses at different pump power. The pulse repetition rate was 145 MHz and the maximum average output power was up to 103 mW with the incident pump power of 10 W.
2. Experimental setup and results The scheme of the experimental setup was shown in Fig. 1. The pump source employed in the experiments was a fiber-coupled 808 nm laser diode with a core diameter of 200 μm. A focusing lens system with a focal length of 75 mm and a coupling efficiency of 93% was used to reimage the pump beam into the laser crystal. The average pump size in the crystal was approximately 400 μm. The active medium was an a-cut 0.2 at% Nd:GdVO4 crystal and the dimensions was 3 3 12 mm. The crystal was high-transmission (HT) coated at 808, 1063 nm, 1.17 μm (499.8%). The laser crystal
40
Z.H. Li et al. / Optics & Laser Technology 58 (2014) 39–42
Focusing optics
Laser diode
M2
M1 Nd:GdVO4
SESAM M3
M5
M6
M4
1.17 μm. It can be used as an output coupler (T¼6%). This subtly design could decrease the mirror loss and increase the slope efficiency even if the mirror coating was not very well. The mode-locked pulses were detected by a high speed InGaAs photo detector (the actual rise of time was about 500 ps), and a digital oscilloscope (LeCroy Wave pro 7300A) with 3 GHz electrical bandwidth. The spectrum was detected by a spectrometer (Andor SR-500I).
1.17 μm
1063 nm Fig. 1. Schematics for mode-locked self-Raman Nd:GdVO4 laser.
1.17 μm
1063 nm
Fig. 2. Pulse trains on two different time scales: 50 ns/div, 5 ns/div; Typical oscilloscope traces for fundamental (bottom) and Raman (top) pulses.
was wrapped with indium foil and mounted in a water-cooled copper holder. The water temperature was controlled to be 20 1C to ensure stable laser output. The mirror M1 was a flat mirror which was anti-reflection (AR) coated at 808 nm (498%) and high-reflection (HR) coated at 1063 nm, 1.17 μm (4 99.8%). The first folded mirror M2 was a spherical mirror with a curvature radius of 500 mm. It was high-reflection (HR) coated at 1063 nm, 1.17 μm (4 99.8%) on the concave surface. The second folded mirror M3 was a spherical mirror with a curvature radius of 200 mm which coatings was as same as M2. The mirror M4 was flat mirror which was high-reflection coated at 1063 nm and 1.17 μm (4 99.8%). And a SESAM was used as a flat cavity mirror. The mirror M6 was used as an optical filter to separate the 1063 nm fundamental laser and the 1.17 μm Raman laser. The splitting mirror M5 was high-reflection coated at 1063 nm and high-transmission coated at 1.17 μm. And it was different from the design of the one used by Weitz [9]. In Ref. [9], the splitting mirror was high-reflection coated at 1.17 μm and high-transmission coated at 1063 nm. However, it is very difficult for ordinary film coating to achieve higher transmission at 1063 nm (T499%) and higher reflection (R499.8%) at 1.17 μm simultaneously. In this case, the 1063 nm fundamental laser loss was relatively high. In our experiment, the splitting mirror M5 was high-reflection coated at 1063 nm. It is easy to achieve reflection higher than 99.8%. In this case, the 1063 nm fundamental laser loss was lower, so that selfRaman laser can be obtained easily. Moreover, the splitting mirror with partial reflection of 1.17 μm Raman laser can be just used as output coupler. The high-transmission dichroic mirror cannot reach 100% transmittance, which was about 97%. The laser was through the mirror twice, so the dichroic mirror was nearly 6% of reflectivity at
Fig. 3. Pulse trains with different incident diode pump power: (a) 7 W, 2 μs/div, 200 ns/div; (b) 8 W, 5 μs/div, 500 ns/div; (c) 9 W, 5 μs/div, 500 ns/div; (d) 10 W, 500 ns/div, 50 ns/div,; demonstrating the amplitude oscillation (pulse repetition rate of 145 MHz).
Z.H. Li et al. / Optics & Laser Technology 58 (2014) 39–42
The amplitude instability was minimized to obtain a relatively stable mode-locking operation with fine adjusting of the cavity. Without an optical filter, the typical time shapes for the fundamental and the Raman pulses are shown in Fig. 2. The bottom of oscilloscope traces was fundamental pulses and the top of the oscilloscope traces was Raman lasers. With an optical filter (1063 nm HT, 1.17 μm HR), the pulse train traces showed on the oscilloscope. Fig. 3(a)–(d) showed the pulse trains on different incident diode pump power. Higher pulse energy fluence results in CW mode locking while a significant lower fluence usually causes Q-switched mode locking. According to the mode-locked equation [12]. No Q-switched mode locking: dRðEp Þ TR TR Ep or ; dEp Ep τ2 τstim
Fig. 4. Pulse trains on two different types of scales: 10 W, 5 ns/div, 500 ps/div.
41
where R is absorber reflective, Ep is per pulse energy, TR is the cavity round trip time, τ2 is the upper state lifetime of the laser, and r is the pump parameter that determines how many times the laser is pumped above threshold. The stimulated lifetime τstim of the upper laser level is given by τstim ¼ τ2 =ðr 1Þ τ2 =r for r b 1. From this equation, higher pump power or longer cavity round trip time could suppress the Q-switched mode locking, the output laser can be CW mode-locked laser. When the incident pump power is increased, it is easier to achieve CW mode locking. Fig. 3(a) and (b) showed the Q-switched mode locking corresponding to the pump power, 7 W and 8 W. When the pump power was up to 9 W, the pulse trains was nearly CW mode locking. Increase the pump power to 10 W, a CW mode locking was achieved. However, it is hard to identify the intensity the threshold of CW mode-locked operation, and 10 W was not exact value, it is only an estimated value. Fig. 3(d) and Fig. 4 showed the mode-locked pulse trains and demonstrated the amplitude stability. The laser amplitude fluctuations were fairly small and stable. The mode-locked self-Raman cavity was 1030 mm in length with pulse period of 6.9 ns. It is matched exactly with the cavity round trip transmit time and corresponded to the repetition rate of 145 MHz. Fig. 4(b) showed a single pulse on the oscilloscope and the pulse width was 503 ps. The actual mode-locked pulse width was less than the estimated pulse duration. Fig. 5 showed the output power at 1.17 μm with respect to the incident pump power. The threshold of self-Raman laser was 5 W. The average output power of the stable CW mode locking was 103 mW. Fig. 6 showed the spectrum of the Nd:GdVO4 1.17 μm self-Raman laser. 3. Conclusions In conclusion, we have designed a novel efficient mode-locked self-Raman Nd:GdVO4 laser in which the pulse repetition rate was 145 MHz. We observed Q-switched mode-locked and stable CW mode-locked at different incident pump power. The maximum average output power was up to 103 mW at an incident pump power of 10 W. A long efficient MHz mode-locked self-Raman Nd: GdVO4 laser at 1.17 μm can be a potential light source for many fields, such as ecological monitoring techniques and medical applications.
Acknowledgements
Fig. 5. Output power at 1.17 μm with respect to the incident diode pump power.
This work has been supported by the National Natural Science Foundation of China (No. 61108021), the Beijing Natural Science Foundation (No. 4102048) and the Fundamental Research Funds for the Central Universities (No. 2013JBM091).
Fig. 6. Spectrum of the Nd:GdVO4 self-Raman laser.
42
Z.H. Li et al. / Optics & Laser Technology 58 (2014) 39–42
References [1] Findeisen J, Eichler HJ, Peuser P. Self-stimulating, transversally diode pumped Nd3 þ :KGd(WO4)2 Raman laser. Opt Commun 2000;181(1):129–33. [2] Omatsu T, Ojima Y, Pask HM, Piper JA, Dekker P. Efficient 1181 nm selfstimulating Raman output from transversely diode-pumped Nd3 þ :KGd(WO4)2 laser. Opt Commun 2004;232(1):327–31. [3] Chen YF. High-power diode-pumped actively Q-switched Nd:YVO4 selfRaman laser: influence of dopant concentration. Opt Lett 2004;29(16):1915–7. [4] Chen YF. Efficient 1521 nm Nd:GdVO4 Raman laser. Opt Lett 2004;29 (22):2632–4. [5] Lee AJ, Pask HM, Dekker P, Piper JA. High efficiency, multi-Watt CW yellow emission from an intracavity-doubled self-Raman laser using Nd:GdVO4. Opt Express 2008;16(26):21958–63. [6] Wang MQ, Ding SH, Yu WY, Zhang WH. High-efficient diode-pumped passively Q-switched c-cut Nd:GdVO4 self-Raman. Laser Phys Lett 2013;10:045403.
[7] Weitz M, Nittmann M, Theobald C, Wallenstein R, Knappe R. Passively Q-switched mode-locked picosecond Nd:YVO4 self-Raman laser, in: Conference on Lasers and Electro-Optics. Optical Society of America; 2006. [8] Peng JY, Zheng Y, Zheng K, Chang XW. Compact Q-switched and mode-locked Nd3 þ :YVO4∕Cr4 þ :YAG self-Raman laser. Appl Opt 2012;51(21):5126–9. [9] Weitz M, Theobald C, Wallenstein R, L'huillier JA. Passively mode-locked picosecond Nd:YVO4 self-Raman laser. Appl Phys Lett 2008;92:091122. [10] Liang HC, Chang HL, Huang WC, Su KW, Chen YF, Chen YT. Self-mode-locked Nd: GdVO4 laser with multi-GHz oscillations: manifestation of third-order nonlinearity. Appl Phys B 2009;97(2):451–5. [11] Keller U, Weingarten KJ, Kärtner FX, Kopf D, Braun B, Jung ID, et al. Semiconductor saturable absorber mirrors (SESAM's) for femtosecond to nanosecond pulse generation in solid-state lasers. IEEE J Sel Top Quantum Electron 1996;2(3):435–53. [12] Kartner FX, Brovelli LR, Kopf D, Kamp M, Calasso I, Keller U. Control of solidstate laser dynamics by semiconductor devices. Opt Eng 1995;34(7):2024–36.
Contents lists available at ScienceDirect
Optics & Laser Technology journal homepage: www.elsevier.com/locate/optlastec
CW mode-locked self-Raman 1.17 μm Nd: GdVO4 laser with a novel long cavity Z.H. Li a,b, J.Y. Peng a,b,n, Y. Zheng a,b a b
Insitute of Laser, School of Science, Beijing Jiaotong University, Beijing 100044, China Key Laboratory of Luminescence and Optical Information, Ministry of Education, Beijing 100044, China
art ic l e i nf o
a b s t r a c t
Article history: Received 18 September 2013 Received in revised form 28 October 2013 Accepted 31 October 2013 Available online 16 November 2013
In this paper we report on a mode-locked self-Raman 1.17 μm Nd:GdVO4 laser. We successfully achieved stable CW mode-locked pulse in a diode-pumped self-Raman Nd:GdVO4 laser with a novel design of cavity included a dichroic mirror used in a special way. With an incident pump power of 10 W, the average output powers was up to 103 mW at a repetition rate of 145 MHz. & 2013 Elsevier Ltd. All rights reserved.
Keywords: Self-Raman Nd:GdVO4 Mode-locked
1. Introduction No matter how new laser materials are continuously developed, only a few wavelengths can be generated directly in solid state laser materials. In recent years frequency shifting of laser pulses by stimulated Stokes Raman scattering in laser crystals has attracted many people's attention, which become a promising method to generate laser efficiently at many new wavelengths. Q-switched and CW (continuous wave) self-Raman lasers based on Nd-doped and Yb-doped laser crystals have been demonstrated, which provide the first Stokes line in the near infrared region between 1100 and 1200 nm [1–6]. With the frequency doubling, these lasers generate radiation at wavelengths in the yellow–orange spectral region, for the use of sodium guide star laser, ecological monitoring techniques, etc. However, few mode-locked self-Raman lasers were reported. The CW mode-locked laser can be used in many fields, such as laser machining, light detection and ranging, nonlinear optical transformation, wind scanner, geo-seismic sensing for oil & gas, etc. In 2006, a passively Q-switched mode-locked Nd:YVO4 self-Raman laser with SESAM was demonstrated by Weitz [7]. In 2012, a Q-switched and mode-locked Nd3 þ :YVO4 self-Raman laser with Cr4 þ :YAG was also achieved by our research group [8]. In 2008, a passively CW mode-locked Nd:YVO4 self-Raman laser was reported by Weitz [9]. As the huge three-order nonlinearity of
n Corresponding author at: Beijing Jiaotong University, Insitute of Laser, School of Science, No. 3 Shang Yuan Cun, Hai Dian Dist, Beijing 100044, China. Tel.: þ 860 105 168 4716. E-mail addresses: [email protected], [email protected] (J.Y. Peng).
0030-3992/$ - see front matter & 2013 Elsevier Ltd. All rights reserved. http://dx.doi.org/10.1016/j.optlastec.2013.10.035
Nd:GdVO4, it is not only relative to the Kerr-lens mode locking [10], but also related to the stimulated Stokes Raman scattering. In this paper, we experimentally demonstrated a CW mode-locked selfRaman Nd:GdVO4 laser with a novel z-shaped cavity included a dichroic mirror used in a different way. The dichroic mirror was used as both the output coupler and splitting mirror. And a SESAM was utilized as the CW mode locked element. As an empirical value for the energy fluence required for stable mode-locked operation is about three to five times the saturation fluence [11], an efficient laser cavity was designed by using the ABCD matrix. We successfully observed stable CW mode-locked self-Raman pulse train in this laser. Moreover, we observed both Q-switched mode-locked and CW mode-locked pulses at different pump power. The pulse repetition rate was 145 MHz and the maximum average output power was up to 103 mW with the incident pump power of 10 W.
2. Experimental setup and results The scheme of the experimental setup was shown in Fig. 1. The pump source employed in the experiments was a fiber-coupled 808 nm laser diode with a core diameter of 200 μm. A focusing lens system with a focal length of 75 mm and a coupling efficiency of 93% was used to reimage the pump beam into the laser crystal. The average pump size in the crystal was approximately 400 μm. The active medium was an a-cut 0.2 at% Nd:GdVO4 crystal and the dimensions was 3 3 12 mm. The crystal was high-transmission (HT) coated at 808, 1063 nm, 1.17 μm (499.8%). The laser crystal
40
Z.H. Li et al. / Optics & Laser Technology 58 (2014) 39–42
Focusing optics
Laser diode
M2
M1 Nd:GdVO4
SESAM M3
M5
M6
M4
1.17 μm. It can be used as an output coupler (T¼6%). This subtly design could decrease the mirror loss and increase the slope efficiency even if the mirror coating was not very well. The mode-locked pulses were detected by a high speed InGaAs photo detector (the actual rise of time was about 500 ps), and a digital oscilloscope (LeCroy Wave pro 7300A) with 3 GHz electrical bandwidth. The spectrum was detected by a spectrometer (Andor SR-500I).
1.17 μm
1063 nm Fig. 1. Schematics for mode-locked self-Raman Nd:GdVO4 laser.
1.17 μm
1063 nm
Fig. 2. Pulse trains on two different time scales: 50 ns/div, 5 ns/div; Typical oscilloscope traces for fundamental (bottom) and Raman (top) pulses.
was wrapped with indium foil and mounted in a water-cooled copper holder. The water temperature was controlled to be 20 1C to ensure stable laser output. The mirror M1 was a flat mirror which was anti-reflection (AR) coated at 808 nm (498%) and high-reflection (HR) coated at 1063 nm, 1.17 μm (4 99.8%). The first folded mirror M2 was a spherical mirror with a curvature radius of 500 mm. It was high-reflection (HR) coated at 1063 nm, 1.17 μm (4 99.8%) on the concave surface. The second folded mirror M3 was a spherical mirror with a curvature radius of 200 mm which coatings was as same as M2. The mirror M4 was flat mirror which was high-reflection coated at 1063 nm and 1.17 μm (4 99.8%). And a SESAM was used as a flat cavity mirror. The mirror M6 was used as an optical filter to separate the 1063 nm fundamental laser and the 1.17 μm Raman laser. The splitting mirror M5 was high-reflection coated at 1063 nm and high-transmission coated at 1.17 μm. And it was different from the design of the one used by Weitz [9]. In Ref. [9], the splitting mirror was high-reflection coated at 1.17 μm and high-transmission coated at 1063 nm. However, it is very difficult for ordinary film coating to achieve higher transmission at 1063 nm (T499%) and higher reflection (R499.8%) at 1.17 μm simultaneously. In this case, the 1063 nm fundamental laser loss was relatively high. In our experiment, the splitting mirror M5 was high-reflection coated at 1063 nm. It is easy to achieve reflection higher than 99.8%. In this case, the 1063 nm fundamental laser loss was lower, so that selfRaman laser can be obtained easily. Moreover, the splitting mirror with partial reflection of 1.17 μm Raman laser can be just used as output coupler. The high-transmission dichroic mirror cannot reach 100% transmittance, which was about 97%. The laser was through the mirror twice, so the dichroic mirror was nearly 6% of reflectivity at
Fig. 3. Pulse trains with different incident diode pump power: (a) 7 W, 2 μs/div, 200 ns/div; (b) 8 W, 5 μs/div, 500 ns/div; (c) 9 W, 5 μs/div, 500 ns/div; (d) 10 W, 500 ns/div, 50 ns/div,; demonstrating the amplitude oscillation (pulse repetition rate of 145 MHz).
Z.H. Li et al. / Optics & Laser Technology 58 (2014) 39–42
The amplitude instability was minimized to obtain a relatively stable mode-locking operation with fine adjusting of the cavity. Without an optical filter, the typical time shapes for the fundamental and the Raman pulses are shown in Fig. 2. The bottom of oscilloscope traces was fundamental pulses and the top of the oscilloscope traces was Raman lasers. With an optical filter (1063 nm HT, 1.17 μm HR), the pulse train traces showed on the oscilloscope. Fig. 3(a)–(d) showed the pulse trains on different incident diode pump power. Higher pulse energy fluence results in CW mode locking while a significant lower fluence usually causes Q-switched mode locking. According to the mode-locked equation [12]. No Q-switched mode locking: dRðEp Þ TR TR Ep or ; dEp Ep τ2 τstim
Fig. 4. Pulse trains on two different types of scales: 10 W, 5 ns/div, 500 ps/div.
41
where R is absorber reflective, Ep is per pulse energy, TR is the cavity round trip time, τ2 is the upper state lifetime of the laser, and r is the pump parameter that determines how many times the laser is pumped above threshold. The stimulated lifetime τstim of the upper laser level is given by τstim ¼ τ2 =ðr 1Þ τ2 =r for r b 1. From this equation, higher pump power or longer cavity round trip time could suppress the Q-switched mode locking, the output laser can be CW mode-locked laser. When the incident pump power is increased, it is easier to achieve CW mode locking. Fig. 3(a) and (b) showed the Q-switched mode locking corresponding to the pump power, 7 W and 8 W. When the pump power was up to 9 W, the pulse trains was nearly CW mode locking. Increase the pump power to 10 W, a CW mode locking was achieved. However, it is hard to identify the intensity the threshold of CW mode-locked operation, and 10 W was not exact value, it is only an estimated value. Fig. 3(d) and Fig. 4 showed the mode-locked pulse trains and demonstrated the amplitude stability. The laser amplitude fluctuations were fairly small and stable. The mode-locked self-Raman cavity was 1030 mm in length with pulse period of 6.9 ns. It is matched exactly with the cavity round trip transmit time and corresponded to the repetition rate of 145 MHz. Fig. 4(b) showed a single pulse on the oscilloscope and the pulse width was 503 ps. The actual mode-locked pulse width was less than the estimated pulse duration. Fig. 5 showed the output power at 1.17 μm with respect to the incident pump power. The threshold of self-Raman laser was 5 W. The average output power of the stable CW mode locking was 103 mW. Fig. 6 showed the spectrum of the Nd:GdVO4 1.17 μm self-Raman laser. 3. Conclusions In conclusion, we have designed a novel efficient mode-locked self-Raman Nd:GdVO4 laser in which the pulse repetition rate was 145 MHz. We observed Q-switched mode-locked and stable CW mode-locked at different incident pump power. The maximum average output power was up to 103 mW at an incident pump power of 10 W. A long efficient MHz mode-locked self-Raman Nd: GdVO4 laser at 1.17 μm can be a potential light source for many fields, such as ecological monitoring techniques and medical applications.
Acknowledgements
Fig. 5. Output power at 1.17 μm with respect to the incident diode pump power.
This work has been supported by the National Natural Science Foundation of China (No. 61108021), the Beijing Natural Science Foundation (No. 4102048) and the Fundamental Research Funds for the Central Universities (No. 2013JBM091).
Fig. 6. Spectrum of the Nd:GdVO4 self-Raman laser.
42
Z.H. Li et al. / Optics & Laser Technology 58 (2014) 39–42
References [1] Findeisen J, Eichler HJ, Peuser P. Self-stimulating, transversally diode pumped Nd3 þ :KGd(WO4)2 Raman laser. Opt Commun 2000;181(1):129–33. [2] Omatsu T, Ojima Y, Pask HM, Piper JA, Dekker P. Efficient 1181 nm selfstimulating Raman output from transversely diode-pumped Nd3 þ :KGd(WO4)2 laser. Opt Commun 2004;232(1):327–31. [3] Chen YF. High-power diode-pumped actively Q-switched Nd:YVO4 selfRaman laser: influence of dopant concentration. Opt Lett 2004;29(16):1915–7. [4] Chen YF. Efficient 1521 nm Nd:GdVO4 Raman laser. Opt Lett 2004;29 (22):2632–4. [5] Lee AJ, Pask HM, Dekker P, Piper JA. High efficiency, multi-Watt CW yellow emission from an intracavity-doubled self-Raman laser using Nd:GdVO4. Opt Express 2008;16(26):21958–63. [6] Wang MQ, Ding SH, Yu WY, Zhang WH. High-efficient diode-pumped passively Q-switched c-cut Nd:GdVO4 self-Raman. Laser Phys Lett 2013;10:045403.
[7] Weitz M, Nittmann M, Theobald C, Wallenstein R, Knappe R. Passively Q-switched mode-locked picosecond Nd:YVO4 self-Raman laser, in: Conference on Lasers and Electro-Optics. Optical Society of America; 2006. [8] Peng JY, Zheng Y, Zheng K, Chang XW. Compact Q-switched and mode-locked Nd3 þ :YVO4∕Cr4 þ :YAG self-Raman laser. Appl Opt 2012;51(21):5126–9. [9] Weitz M, Theobald C, Wallenstein R, L'huillier JA. Passively mode-locked picosecond Nd:YVO4 self-Raman laser. Appl Phys Lett 2008;92:091122. [10] Liang HC, Chang HL, Huang WC, Su KW, Chen YF, Chen YT. Self-mode-locked Nd: GdVO4 laser with multi-GHz oscillations: manifestation of third-order nonlinearity. Appl Phys B 2009;97(2):451–5. [11] Keller U, Weingarten KJ, Kärtner FX, Kopf D, Braun B, Jung ID, et al. Semiconductor saturable absorber mirrors (SESAM's) for femtosecond to nanosecond pulse generation in solid-state lasers. IEEE J Sel Top Quantum Electron 1996;2(3):435–53. [12] Kartner FX, Brovelli LR, Kopf D, Kamp M, Calasso I, Keller U. Control of solidstate laser dynamics by semiconductor devices. Opt Eng 1995;34(7):2024–36.