#
Efficient Dual-Wavelengths Continuous Mode Lasers by End-Pumping of Series Nd:YVO_{4} and Nd:GdVO_{4} Crystals and Speckle Reduction Study

^{*}

## Abstract

**:**

## 1. Introduction

## 2. Experiments

#### 2.1. Dual-Wavelength Laser Setup

_{0}) of 120 µm.

_{o}) was varied along the optical axis (in z direction) through the cavity, allowing for the control of the gain and pumping absorption efficiency of each crystal [17]. z

_{o}= 0 was defined as the input facet (or ${M}_{1}$) of $L{C}_{1}$. The pump absorption efficiency of each crystal was also controlled by altering the pumping wavelength (${\lambda}_{p}$) which was achieved by changing the temperature of the LD.

#### 2.2. Tri/Quad Wavelength Laser Setup

#### 2.3. The Speckle Contrast Imaging Configuration

## 3. Results and Discussions

#### 3.1. Dual Output Wavelengths

^{2}was factor < 1.2 for 1062.4 nm and 1063.7 nm.

#### 3.2. Tri and Quad Output Wavelengths Emission

^{2}factor was measured to be <2; it was obvious that the quality of the total output lasers from each case became worse.

## 4. Conclusions

## Author Contributions

## Funding

## Conflicts of Interest

## References

- Liu, Y.; Zhong, K.; Mei, J.; Wang, M.; Guo, S.; Liu, C.; Xu, D.; Shi, W.; Yao, J. Compact and flexible dual-wavelength laser generation in coaxial diode-end-pumped configuration. IEEE Photonics J.
**2017**, 9, 1–10. [Google Scholar] [CrossRef] - Ding, Y.J. Progress in terahertz sources based on difference-frequency generation. J. Opt. Soc. Am. B
**2014**, 31, 2696–2711. [Google Scholar] [CrossRef] - Liu, Y.; Zhong, K.; Mei, J.; Liu, C.; Shi, J.; Ding, X.; Xu, D.; Shi, W.; Yao, J. Compact and stable high-repetition-rate terahertz generation based on an efficient coaxially pumped dual-wavelength laser. Opt. Express
**2017**, 25, 23368–23375. [Google Scholar] [CrossRef] [PubMed] - Genina, E.A.; Bashkatov, A.N.; Simonenko, G.V.; Odoevskaya, O.D.; Tuchin, V.V.; Altshuler, G.B. Low-intensity indocyanine-green laser phototherapy of acne vulgaris: Pilot study. J. Biomed. Opt.
**2004**, 9, 828–835. [Google Scholar] [CrossRef] [PubMed] - Chen, Y.F.; Chen, Y.S.; Tsai, S.W. Diode-pumped Q-switched laser with intracavity sum frequency mixing in periodically poled KTP. Appl. Phys. B
**2004**, 79, 207–210. [Google Scholar] [CrossRef] - Son, S.N.; Song, J.J.; Kang, J.U.; Kim, C.S. Simultaneous second harmonic generation of multiple wavelength laser outputs for medical sensing. Sensors
**2011**, 11, 6125–6130. [Google Scholar] [CrossRef] - Shen, B.; Jin, L.; Zhang, J.; Tian, J. Simultaneous tri-wavelength laser operation at 916, 1086, and 1089 nm of diode-pumped Nd:LuVO
_{4}crystal. Laser Phys.**2016**, 26. [Google Scholar] [CrossRef] - Demirbas, U.; Uecker, R.; Fujimoto, J.G.; Leitenstorfer, A. Multicolor lasers using birefringent filters: Experimental demonstration with Cr:Nd:GSGG and Cr:LiSAF. Opt. Express
**2017**, 25, 2594. [Google Scholar] [CrossRef] - Maestre, H.; Torregrosa, A.J.; Pereda, J.A.; Fernández-Pousa, C.R.; Capmany, J. Dual-wavelength Cr
^{3+}:LiCaAlF_{6}solid-state laser with tunable THz frequency difference. IEEE J. Quantum Electron.**2010**, 46, 1681–1685. [Google Scholar] [CrossRef] - Sirotkin, A.A.; Vlasov, V.I.; Zagumennyi, A.I.; Zavartsev, Y.D.; Kutovoi, S.A.; Shcherbakov, I.A. Control of the spectral parameters of vanadate lasers. Quantum Electron.
**2014**, 44, 7–12. [Google Scholar] [CrossRef] - Zhao, P.; Ragam, S.; Ding, Y.J.; Zotova, I.B. Investigation of terahertz generation from passively Q-switched dual-frequency laser pulses. Opt. Lett.
**2011**, 36, 4818–4820. [Google Scholar] [CrossRef] [PubMed] - Pallas, F.; Herault, E.; Roux, J.-F.; Kevorkian, A.; Coutaz, J.-L.; Vitrant, G. Simultaneous passively Q-switched dual-wavelength solid-state laser working at 1065 and 1066 nm. Opt. Lett.
**2012**, 37, 2817–2819. [Google Scholar] [CrossRef] [PubMed] - Xu, B.; Wang, Y.; Lin, Z.; Cui, S.; Cheng, Y.; Xu, H.; Cai, Z. Efficient and compact orthogonally polarized dual-wavelength Nd: YVO
_{4}laser at 1342 and 1345 nm. Appl. Opt.**2016**, 55, 42–46. [Google Scholar] [CrossRef] [PubMed] - Huang, Y.J.; Tzeng, Y.S.; Tang, C.Y.; Chiang, S.Y.; Liang, H.C.; Chen, Y.F. Efficient high-power terahertz beating in a dual-wavelength synchronously mode-locked laser with dual gain media. Opt. Lett.
**2014**, 39, 1477–1480. [Google Scholar] [CrossRef] [PubMed] - Huang, Y.J.; Tzeng, Y.S.; Cho, H.H.; Chen, Y.F. Effect of spatial hole burning on a dual-wavelength mode-locked laser based on compactly combined dual gain media. Photonics Res.
**2014**, 2, 161–167. [Google Scholar] [CrossRef] - Tran, T.-T.-K.; Svensen, Ø.; Chen, X.; Nadeem Akram, M. Speckle reduction in laser projection displays through angle and wavelength diversity. Appl. Opt.
**2016**, 55, 1267–1274. [Google Scholar] [CrossRef] [PubMed] - Pallas, F.; Herault, E.; Zhou, J.; Roux, J.F.; Vitrant, G. Stable dual-wavelength microlaser controlled by the output mirror tilt angle. Appl. Phys. Lett.
**2011**, 99, 2–5. [Google Scholar] [CrossRef] - Sato, Y.; Taira, T. Spectroscopic properties of neodymium-doped yttrium orthovanadate single crystals with high-resolution measurement. Jpn. J. Appl. Phys.
**2002**, 41, 5999–6002. [Google Scholar] [CrossRef] - Ma, Q.; Xu, C.Q. Wavelength blending with reduced speckle and improved color for laser projection. Opt. Lasers Eng.
**2017**, 97, 27–33. [Google Scholar] [CrossRef] - Akram, M.N.; Chen, X. Speckle reduction methods in laser-based picture projectors. Opt. Rev.
**2016**, 23, 108–120. [Google Scholar] [CrossRef] - Chen, H.; Huang, Y.; Li, B.; Liao, W.; Zhang, G.; Lin, Z. Efficient orthogonally polarized dual-wavelength Nd:LaMgB
_{5}O_{10}laser. Opt. Lett.**2015**, 40, 4659–4662. [Google Scholar] [CrossRef] [PubMed] - Wang, D.Z.; Yan, B.X.; Bi, Y.; Sun, D.H.; Sang, Y.H.; Liu, H.; Kumar, A.; Boughton, R.I. Three-wavelength green laser using intracavity frequency conversion of Nd:Mg:LiTaO
_{3}with a MgO:PPLN crystal. Appl. Phys. B**2014**, 117, 1117–1121. [Google Scholar] [CrossRef]

**Figure 1.**Experimental setup used in the measurements: (

**a**) diagram for end pumping series crystals laser and (

**b**) schematic diagram for σ-π configurations.

**Figure 2.**Configuration of $L{C}_{1}$ and $L{C}_{2}$ in multi wavelength emission. (

**a**) A 3D configuration with a tilted angle of θ for ${M}_{2}$, and (

**b**) xy-view of the setup for tri output wavelengths emission with θ = 0.7 mrad and ∅ = 0 rad (left) and quad wavelengths emission (right) with θ = 0.7 mrad and ∅ = 0.78 rad.

**Figure 4.**(

**a**) and (

**b**) are the single (1063.7 nm) and dual-wavelength normalized emission spectrum respectively.

**Figure 5.**The measured output powers of 1062.4 nm (triangle up) and 1063.7 nm (dots) for σ-π configuration.

**Figure 6.**The measured output power versus pump power for σ-π configuration, where the total output power, output power for 1062.4 nm, and 1063.7 nm are represented by black dots, red triangle up, and blue square, respectively.

**Figure 8.**The measured (

**a**) total power for σ-π configuration, (

**b**) power of 1063.7 nm in σ- polarization, (

**c**) power of 1062.4 nm in π- polarization.

**Figure 10.**The speckle contrast ratio (SCR) as a function of normalized power (P

_{λ2}/(P

_{λ1}+P

_{λ2})).

**Figure 11.**The measured output spectrum of (

**a**) tri-wavelength emission at 1062.4 nm, 1063.6 nm, and 1064.6 nm, and (

**b**) quad-wavelength emission at 1062.3 nm, 1063.6 nm, 1064.5 nm, and 1066.1 nm.

© 2019 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (http://creativecommons.org/licenses/by/4.0/).

## Share and Cite

**MDPI and ACS Style**

Mohamed, M.; Zhang, B.; Ma, Q.; Kneller, J.; Xu, C.-Q. Efficient Dual-Wavelengths Continuous Mode Lasers by End-Pumping of Series *Nd*:*YVO*_{4} and *Nd*:*GdVO*_{4} Crystals and Speckle Reduction Study. *Photonics* **2019**, *6*, 53.
https://doi.org/10.3390/photonics6020053

**AMA Style**

Mohamed M, Zhang B, Ma Q, Kneller J, Xu C-Q. Efficient Dual-Wavelengths Continuous Mode Lasers by End-Pumping of Series *Nd*:*YVO*_{4} and *Nd*:*GdVO*_{4} Crystals and Speckle Reduction Study. *Photonics*. 2019; 6(2):53.
https://doi.org/10.3390/photonics6020053

**Chicago/Turabian Style**

Mohamed, Mahmoud, Bin Zhang, Qianli Ma, Josh Kneller, and Chang-Qing Xu. 2019. "Efficient Dual-Wavelengths Continuous Mode Lasers by End-Pumping of Series *Nd*:*YVO*_{4} and *Nd*:*GdVO*_{4} Crystals and Speckle Reduction Study" *Photonics* 6, no. 2: 53.
https://doi.org/10.3390/photonics6020053