## Enhanced output power for phase-matched second-harmonic generation at 10.6 μm in a ZnGeP_{2} crystal

Optics Express, Vol. 15, Issue 20, pp. 12699-12707 (2007)

http://dx.doi.org/10.1364/OE.15.012699

Acrobat PDF (219 KB)

### Abstract

Second-harmonic generation was phase-matched at the fundamental wavelength of 10.6 μm in an annealed ZnGeP_{2} crystal at room temperature. Our results demonstrated that the phase-matching angle was decreased with increasing the pump power. Such a unique dependence resulted in a significant enhancement on the second-harmonic output power. The highest average output power at 5.3 μm was 55 mW for an average pump power of 5.0 W, which corresponded to a conversion efficiency of 1.1%. Due to the laser-induced heating effect, the second-harmonic output power was increased by 65%. Such an efficient conversion was made possible also by using a short-pulse repetition-frequency-excited waveguide and single-longitudinal-mode CO_{2} laser as a fundamental beam.

© 2007 Optical Society of America

## 1. Introduction

_{2}laser produces radiations at a number of wavelengths in the range of 9.2-11.4 μm. Second-harmonic generation (SHG) using the output of such a laser as a fundamental beam can extend the output wavelengths down to the range of 4.6-5.8 μm. Such a frequency conversion still plays an important role for the efficient generation of mid-IR frequencies since other approaches such as quantum-cascade lasers produce relatively low powers at the emission wavelengths below 5.4 μm at room temperature. To successfully achieve an efficient conversion from the CO

_{2}laser frequencies, one needs a nonlinear medium with a large figure of merit. In the past, a series of nonlinear materials were studied such as GaSe [1

1. D. R. Suhre, N. B. Singh, V. Balakrishna, N. C. Fernelius, and F. K. Hopkins, “Improved crystal quality and harmonic generation in GaSe doped with indium,” Opt. Lett. **22**, 775–777 (1997). [CrossRef] [PubMed]

_{2}[2

2. G. B. Abdullaev, K. R. Allakhverdiev, M. E. Karasev, V. I. Konov, L. A. Kulevskii, N. B. Mustafaev, P. P. Pashinin, A. M. Prokhorov, Yu. M. Starodumov, and N. I. Chapliev, “Efficient generation of the second harmonic of CO_{2} laser radition in a GaSe crystal,” Sov. J. Quantum Electron. **19**, 494–498 (1989). [CrossRef]

_{2}[3

3. N. Menyuk, G. W. Iseler, and A. Mooradian, “High-efficiency high-average-power second-harmonic generation with CdGeAs_{2},” Appl. Phys. Lett. **29**, 422–424 (1971). [CrossRef]

_{2}[4

4. A. Harasaki and K. Kato, “New data on the nonlinear optical constant, phase-matching, and optical damage of AgGaS_{2},” Jpn. J. Appl. Phys. **36**, 700–703 (1997). [CrossRef]

_{2}[5

5. R. Eckardt, Y. Fan, R. Byer, R. Route, R. Feigeison, and J. Laan, “Efficient second harmonic generation of 10- μm radiation in AgGaSe_{2},” Appl. Phys. Lett. **47**, 786–788 (1985). [CrossRef]

_{2}has produced the highest conversion efficiency out of these four nonlinear-optical crystals for the same pump power [5

5. R. Eckardt, Y. Fan, R. Byer, R. Route, R. Feigeison, and J. Laan, “Efficient second harmonic generation of 10- μm radiation in AgGaSe_{2},” Appl. Phys. Lett. **47**, 786–788 (1985). [CrossRef]

_{2}has a potential for SHG from CO

_{2}lasers since it possesses a wide transparency range (0.74-12 μm) and a large nonlinear coefficient (d

_{36}≈ 75 pm/V). Therefore, such a crystal has been used for frequency-doubling CO

_{2}laser radiations and implementing optical parametric oscillators [6

6. P. B. Phua, B. S. Tan, R. F. Wu, K. S. Lai, L. Chia, and E. Lau, “High-average-power mid-infrared ZnGeP_{2} optical parametric oscillators with a wavelength-dependent polarization rotator,” Opt. Lett. **31**, 489–491 (2006). [CrossRef] [PubMed]

_{2}crystal by using an extremely high peak power of the fundamental beam [7

7. Yu. M. Andreev, V. Yu. Baranov, V. G. Voevodin, P. P. Geiko, A. I. Bribenyukov, S. V. Izyumov, S. M. Kozochkin, V. D. Pis’mennyi, Yu. A. Satov, and A. P. Strel’tsov, “Efficient generation of the second harmonic of a nanosecond CO_{2} laser radiation pulse,” Sov. J. Quantum Electron. **17**, 1435–1436 (1987). [CrossRef]

_{2}crystal, most papers claimed that it is not possible to phase-match SHG at 10.6 μm from a ZnGeP

_{2}crystal [2

2. G. B. Abdullaev, K. R. Allakhverdiev, M. E. Karasev, V. I. Konov, L. A. Kulevskii, N. B. Mustafaev, P. P. Pashinin, A. M. Prokhorov, Yu. M. Starodumov, and N. I. Chapliev, “Efficient generation of the second harmonic of CO_{2} laser radition in a GaSe crystal,” Sov. J. Quantum Electron. **19**, 494–498 (1989). [CrossRef]

8. G. D. Boyd and F. G. Stortz, “Linear and nonlinear optical properties of ZnGeP_{2} and CdSe,” Appl. Phys. Lett. **18**, 301–303 (1971). [CrossRef]

9. G. C. Bhar and G. C. Ghosh, “Temperature dependent phase-matched nonlinear optical devices using CdSe and ZnGeP_{2},” IEEE J. Quantum Electron. **16**, 838–843 (1980). [CrossRef]

10. F. Madarasz, J. Dimmock, D. Dietz, and K. Bachmann, “Sellmeier paprameters for ZnGeP_{2} and GaP,” J. Appl. Phys. **87**, 1564–1565 (2000). [CrossRef]

12. K. Kato, “Second-harmonic and sum-frequency generation in ZnGeP_{2},” Appl. Opt. **36**, 2506–2510 (1997). [CrossRef] [PubMed]

13. S. Das, G. Bhar, S. Gangopadhyay, and C. Ghosh, “Linear and nonlinear optical properties of ZngeP_{2} crystal for infrared laser device applications: revisited,” Appl. Opt. **42**, 4335–4340 (2003). [CrossRef] [PubMed]

_{2}crystal at room temperature. Since only a few crystals can be practically used to achieve SHG at 10.6 μm, the investigation of the phase-matching condition for SHG at 10.6 μm in a ZnGeP

_{2}crystal is important.

_{2}laser in a ZnGeP

_{2}crystal at room temperature. In terms of linear and nonlinear optical properties, this crystal is quite similar to those investigated previously [14

14. D. E. Zelmon, E. A. Hanning, and P. G. Schunemann, “Refractive-index measurements and Sellmeier coefficients for zinc germanium phosphide form 2 to 9 μm with implications for phase matching in optical frequency-conversion devices,” J. Opt. Soc. Am. B **18**, 1307–1310 (2001). [CrossRef]

15. W. Shi, Y. J. Ding, and P. G. Schunemann, “Coherent terahertz waves based on difference-frequency generation in an annealed zinc-germanium phosphide crystal: improvements on tuning ranges and peak powers,” Opt. Commun. **233**, 183–189 (2004). [CrossRef]

_{2}laser radiation in a ZnGeP

_{2}crystal can be used to produce a peak power as high as 127 W following our experimental result. Out of the total output power of 127 W, 50 W originate from the laser-induced heating effect, which is amounted to 65% increase in the output power. Moreover, such a high-power source does not require any cooling device.

## 2. Experimental details

_{2}crystal having dimensions of 14×15×20.6 mm

^{3}was cut and polished along

*x*axis. It was mounted on a rotational stage for rotating it around

*y*axis with an angle resolution of 0.1°. A fundamental beam was propagating in the

*x-z*plane with its polarization lying in the x-z plane. Such a configuration corresponds to an

*ee-o*type-I phase-matching configuration, where

*e*and

*o*specify the extraordinary and ordinary polarizations for the fundamental and SH beams inside the ZnGeP

_{2}crystal, respectively. A short-pulse repetition-frequency-excited CO

_{2}waveguide laser was used as a pump beam. Such a laser system was lasing at a single longitudinal mode. Its pulse width was measured to be 12 ns; its repetition rate was adjustable from 0 to 100 kHz; its linewidth was about 100 MHz. For our SHG study, we set the repetition rate to 60 kHz. The average output power can be continuously increased from 0 W to 5 W by using a λ/2 plate and a polarizer. A short-pass filter was placed behind the ZnGeP

_{2}crystal to cut off the transmitted (i.e. un-converted) 10.6 μm radiation. A photovoltaic detector was used to investigate the characteristics of the SHG. The SH output powers were measured by using a power meter.

## 3. Results and discussions

_{2}crystal using a FTIR system within a wavelength range from 2 μm to 12 μm, see inset to Fig. 1. The transmittances reduced by the losses through the Fresnel reflections of the entrance and exit facets for the infrared beam were obtained by using the Sellmeier equation given in Ref. [16

16. G. C. Bhar, L. K. Samanta, D. K. Ghosh, and S. Das, “Tunable parametric ZnGeP_{2} crystal oscillator,” Sov. J. Quantum Electron. **17**, 860–861 (1987). [CrossRef]

^{-1}and 0.15 cm

^{-1}at 10.6 μm and 5.3 μm, respectively. One can see that since the absorption coefficient for the fundamental beam is much higher, it should be used to determine the optimum length of the ZnGeP

_{2}crystal when a SHG experiment is designed.

16. G. C. Bhar, L. K. Samanta, D. K. Ghosh, and S. Das, “Tunable parametric ZnGeP_{2} crystal oscillator,” Sov. J. Quantum Electron. **17**, 860–861 (1987). [CrossRef]

_{2}crystals to the best of our knowledge.

_{2}crystal has a relatively large absorption coefficient at 10.6 μm. Therefore, a significant amount of the input power for the fundamental beam was absorbed by the crystal, followed by the conversion of the absorbed energy into heat. Such a laser-induced heating effect in the crystal results in the increase of the temperature of the crystal. Based on Ref. [8

8. G. D. Boyd and F. G. Stortz, “Linear and nonlinear optical properties of ZnGeP_{2} and CdSe,” Appl. Phys. Lett. **18**, 301–303 (1971). [CrossRef]

_{2}crystal strongly depend on the temperature of the crystal:

12. K. Kato, “Second-harmonic and sum-frequency generation in ZnGeP_{2},” Appl. Opt. **36**, 2506–2510 (1997). [CrossRef] [PubMed]

12. K. Kato, “Second-harmonic and sum-frequency generation in ZnGeP_{2},” Appl. Opt. **36**, 2506–2510 (1997). [CrossRef] [PubMed]

*C*

_{p}is the heat capacity,

*P*

_{1}is the peak power of each fundamental pulse, τ

_{1}is the pulse width of each fundamental pulse,

*T*

_{1}is the transmittance for the fundamental beam propagating through the entrance facet, α

_{1}is the absorption coefficient at 10.6 μm, and

*w*is the beam radius for the fundamental beam. For

*C*

_{p}≈ 464 J/kg∙K, ρ ≈ 4.12 g/cm

^{3},

*P*

_{1}≈ 6.9 kW, τ

_{1}≈ 12 ns, α

_{1}≈ 0.76 cm

^{-1},

*T*

_{1}≈ 0.74, and

*w*≈ 0.2 mm, (Δ

*T*)

_{max}is estimated to be 0.019 K. This implies that in order to produce a temperature rise of 51 K the number of pulses required on the fundamental beam required is at least 2600. Based on such an estimate, heat dissipation has played an important role after such a large number of the laser pulses. A more accurate determination of the temperature distribution within the ZnGeP

_{2}crystal will require an extensive effort on numerical modeling and experiments, which is beyond the scope of this paper.

_{2}crystal, the phase-matching condition is given by

*n*

_{e}^{ω}=

*n*

_{o}^{2ω}, where

*n*

_{e}^{ω}and

*n*

_{o}^{2ω}are the extraordinary and ordinary refractive indices for the fundamental and SH waves, respectively, see Fig. 5. When the crystal is heated up by absorbing some portion of the fundamental beam, the extraordinary refractive index is increased by an amount larger than the ordinary refractive index. Such a difference in the increases of the refractive indices for two different polarizations results in the enhancement of the birefringence for the ZnGeP

_{2}crystal, and therefore, the decrease of the phase-matching angle, see Fig. 5. We would like to emphasize that even without any laser-induced heating effect the SHG can be still phase-matched at an angle measured to be 84.9°±0.03°, see Fig. 2.

*θ*, see Fig. 6. One can see from Fig. 6 that the SH output powers measured by us are higher than those predicted by a quadratic dependence. Indeed, at the highest input power of 5.0 W, the average SH output power reached 55 mW whereas the peak power was 127 W. This peak power was actually 50 W higher than the value predicted by using the quadratic dependence, which implies that this amount of the output power was added after the laser-induced heating effect. For the

*ee-o*phase-matching configuration in a ZnGeP

_{2}crystal, the effective second-order nonlinear coefficient is given by

*d*

_{eff}=

*d*

_{36}sin(2

*θ*). Based on such an expression, one can see that when the phase-matching angle of below and close to 90° is decreased, the effective second-order nonlinear coefficient is increased. Consequently, the SH output power is also increased. By incorporating the measured values of

*θ*into our data, we have modified the quadratic dependence illustrated in Fig. 6. One can see from Fig. 6 that the modified dependence fits our experimental values quite well. According to our experimental result, the conversion efficiency for the input power of the fundamental beam to be 5.0 W was 1.1% (a normalized conversion efficiency of 110% MW

^{-1}∙cm

^{-1}).

*P*

_{2}is the SH peak power,

*L*is the crystal length, λ

_{2}is the wavelength of the SH beam,

*T*

_{2}is the Fresnel transmittance for the SH beam, and α

_{2}is the absorption coefficient for the SH beam. For

*L*≈ 14 mm,

*w*≈ 0.2 mm, α

_{1}≈ 0.76 cm

^{-1}, and α

_{2}≈ 0.15 cm

^{-1}, the conversion efficiency was calculated to be 1.9%, which in a very good agreement with our measured value.

## 4. Comparison with previous results

10. F. Madarasz, J. Dimmock, D. Dietz, and K. Bachmann, “Sellmeier paprameters for ZnGeP_{2} and GaP,” J. Appl. Phys. **87**, 1564–1565 (2000). [CrossRef]

16. G. C. Bhar, L. K. Samanta, D. K. Ghosh, and S. Das, “Tunable parametric ZnGeP_{2} crystal oscillator,” Sov. J. Quantum Electron. **17**, 860–861 (1987). [CrossRef]

_{2},” Appl. Opt. **36**, 2506–2510 (1997). [CrossRef] [PubMed]

_{2}laser we used was lasing at the single longitudinal mode, it had a very narrow linewidth of ∼ 100 MHz (∼ 0.037 nm at 10.6 μm), which was much narrower than most of the CO

_{2}lasers used for frequency doubling in ZnGeP

_{2}crystals in the past. Second, as illustrated in Fig. 3, the temporal profile of our CO

_{2}laser is nearly symmetric unlike a TEA CO

_{2}laser system which typically has a temporal profile of a 100 ns-long spike followed by a 1-μs-long tail. Because of the superior performance of our CO

_{2}laser, an efficient frequency conversion was achieved from the annealed ZnGeP

_{2}crystal. As summarized above, the highest conversion efficiency achieved by us was 1.1% for a peak intensity of 5.5 MW/cm

^{2}(a peak power of 6.9 kW) in a 14-mm-long ZnGeP

_{2}crystal. In comparison, the conversion efficiency for a 15-mm-long GaSe crystal was measured to be about 3.0% under the same experimental conditions, which is a factor of 2.7 higher. Third, the phase-matching wavelength for the fundamental beam is now extended to 10.6 μm. According to Ref. [2

2. G. B. Abdullaev, K. R. Allakhverdiev, M. E. Karasev, V. I. Konov, L. A. Kulevskii, N. B. Mustafaev, P. P. Pashinin, A. M. Prokhorov, Yu. M. Starodumov, and N. I. Chapliev, “Efficient generation of the second harmonic of CO_{2} laser radition in a GaSe crystal,” Sov. J. Quantum Electron. **19**, 494–498 (1989). [CrossRef]

_{2}crystal. Therefore, the normalized conversion efficiency obtained previously [2

_{2} laser radition in a GaSe crystal,” Sov. J. Quantum Electron. **19**, 494–498 (1989). [CrossRef]

^{-1}∙cm

^{-1}. This value is a factor of 5 lower than the value measured in our experiment, i.e. 110% MW

^{-1}∙cm

^{-1}.

^{2}, (a peak power of 10 MW) the conversion efficiency was measured to be 49% in a 3-mm-long ZnGeP

_{2}crystal at the fundamental wavelength of 9.52 μm [7

7. Yu. M. Andreev, V. Yu. Baranov, V. G. Voevodin, P. P. Geiko, A. I. Bribenyukov, S. V. Izyumov, S. M. Kozochkin, V. D. Pis’mennyi, Yu. A. Satov, and A. P. Strel’tsov, “Efficient generation of the second harmonic of a nanosecond CO_{2} laser radiation pulse,” Sov. J. Quantum Electron. **17**, 1435–1436 (1987). [CrossRef]

_{2}crystal from our result based on linear scaling with the crystal length. After considering the spatial depletion for the fundamental beam, we have estimated the conversion efficiency from our crystal to be 53% when the input power of the fundamental beam is increased from 6.9 kW to 10 MW. This estimated value is quite close to that measured in Ref. [7

7. Yu. M. Andreev, V. Yu. Baranov, V. G. Voevodin, P. P. Geiko, A. I. Bribenyukov, S. V. Izyumov, S. M. Kozochkin, V. D. Pis’mennyi, Yu. A. Satov, and A. P. Strel’tsov, “Efficient generation of the second harmonic of a nanosecond CO_{2} laser radiation pulse,” Sov. J. Quantum Electron. **17**, 1435–1436 (1987). [CrossRef]

## 5. Conclusion

_{2}crystal. Our experimental result demonstrates that the phase-matching angle is decreased with increasing the input power of the fundamental beam. Such a decrease in the phase-matching angle is caused by heating of the crystal induced by the significant absorption of the fundamental laser beam. The decrease of the phase-matching angle has been used by us to enhance the SH output powers and conversion efficiencies. For an input power of the fundamental beam to be 5.0 W, the SH output power was measured to be 55 mW which corresponds to a peak power of 127 W at 5.3 μm. It is worth noting that 39% of the generated SH power was provided by the laser-induced heating effect. The highest conversion efficiency for the SHG was measured to be 1.1%. Although other crystals such as AgGaSe

_{2}can be used to produce much higher conversion efficiencies for the SHG the CO

_{2}laser at the emission wavelength of 10.6 μm, our results indicated that ZnGeP

_{2}crystal can be also used to achieve phase-matched SHG at 10.6 μm.

_{3}[18

18. X. Mu and Y. J. Ding, “Optical-parametric generation and oscillation in periodically-poled lithium niobate in the presence of strong two-photon absorption,” Opt. Commun. **242**, 305–312 (2004). [CrossRef]

_{2}lasers, one can produce the SH outputs with the wavelengths in the range of 4.6-5.8 μm. Therefore, such a frequency conversion device may be useful to countermeasures.

## Acknowledgments

_{2}crystal. This work has been supported by U.S. AFOSR.

## References and links

1. | D. R. Suhre, N. B. Singh, V. Balakrishna, N. C. Fernelius, and F. K. Hopkins, “Improved crystal quality and harmonic generation in GaSe doped with indium,” Opt. Lett. |

2. | G. B. Abdullaev, K. R. Allakhverdiev, M. E. Karasev, V. I. Konov, L. A. Kulevskii, N. B. Mustafaev, P. P. Pashinin, A. M. Prokhorov, Yu. M. Starodumov, and N. I. Chapliev, “Efficient generation of the second harmonic of CO |

3. | N. Menyuk, G. W. Iseler, and A. Mooradian, “High-efficiency high-average-power second-harmonic generation with CdGeAs |

4. | A. Harasaki and K. Kato, “New data on the nonlinear optical constant, phase-matching, and optical damage of AgGaS |

5. | R. Eckardt, Y. Fan, R. Byer, R. Route, R. Feigeison, and J. Laan, “Efficient second harmonic generation of 10- μm radiation in AgGaSe |

6. | P. B. Phua, B. S. Tan, R. F. Wu, K. S. Lai, L. Chia, and E. Lau, “High-average-power mid-infrared ZnGeP |

7. | Yu. M. Andreev, V. Yu. Baranov, V. G. Voevodin, P. P. Geiko, A. I. Bribenyukov, S. V. Izyumov, S. M. Kozochkin, V. D. Pis’mennyi, Yu. A. Satov, and A. P. Strel’tsov, “Efficient generation of the second harmonic of a nanosecond CO |

8. | G. D. Boyd and F. G. Stortz, “Linear and nonlinear optical properties of ZnGeP |

9. | G. C. Bhar and G. C. Ghosh, “Temperature dependent phase-matched nonlinear optical devices using CdSe and ZnGeP |

10. | F. Madarasz, J. Dimmock, D. Dietz, and K. Bachmann, “Sellmeier paprameters for ZnGeP |

11. | K. Kato, E. Takaoka, and N. Umemura, “New sellmeier and thermo-optic dispersion formulas for ZnGeP |

12. | K. Kato, “Second-harmonic and sum-frequency generation in ZnGeP |

13. | S. Das, G. Bhar, S. Gangopadhyay, and C. Ghosh, “Linear and nonlinear optical properties of ZngeP |

14. | D. E. Zelmon, E. A. Hanning, and P. G. Schunemann, “Refractive-index measurements and Sellmeier coefficients for zinc germanium phosphide form 2 to 9 μm with implications for phase matching in optical frequency-conversion devices,” J. Opt. Soc. Am. B |

15. | W. Shi, Y. J. Ding, and P. G. Schunemann, “Coherent terahertz waves based on difference-frequency generation in an annealed zinc-germanium phosphide crystal: improvements on tuning ranges and peak powers,” Opt. Commun. |

16. | G. C. Bhar, L. K. Samanta, D. K. Ghosh, and S. Das, “Tunable parametric ZnGeP |

17. | V. G. Dmitriviev, G. G. Gurzadyan, and D. N. Nikogosyan, |

18. | X. Mu and Y. J. Ding, “Optical-parametric generation and oscillation in periodically-poled lithium niobate in the presence of strong two-photon absorption,” Opt. Commun. |

**OCIS Codes**

(190.2620) Nonlinear optics : Harmonic generation and mixing

(190.4400) Nonlinear optics : Nonlinear optics, materials

**ToC Category:**

Nonlinear Optics

**History**

Original Manuscript: August 14, 2007

Revised Manuscript: September 6, 2007

Manuscript Accepted: September 16, 2007

Published: September 19, 2007

**Citation**

Yi Jiang and Yujie J. Ding, "Enhanced output power for phase-matched second-harmonic generation at 10.6 μm in a ZnGeP_{2} crystal," Opt. Express **15**, 12699-12707 (2007)

http://www.opticsinfobase.org/oe/abstract.cfm?URI=oe-15-20-12699

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### References

- D. R. Suhre, N. B. Singh, V. Balakrishna, N. C. Fernelius, and F. K. Hopkins, "Improved crystal quality and harmonic generation in GaSe doped with indium," Opt. Lett. 22, 775-777 (1997). [CrossRef] [PubMed]
- G. B. Abdullaev, K. R. Allakhverdiev, M. E. Karasev, V. I. Konov, L. A. Kulevskii, N. B. Mustafaev, P. P. Pashinin, A. M. Prokhorov, Yu. M. Starodumov, and N. I. Chapliev, "Efficient generation of the second harmonic of CO2 laser radition in a GaSe crystal," Sov. J. Quantum Electron. 19, 494-498 (1989). [CrossRef]
- N. Menyuk, G. W. Iseler, and A. Mooradian, "High-efficiency high-average-power second-harmonic generation with CdGeAs2," Appl. Phys. Lett. 29, 422-424 (1971). [CrossRef]
- A. Harasaki and K. Kato, "New data on the nonlinear optical constant, phase-matching, and optical damage of AgGaS2," Jpn. J. Appl. Phys. 36, 700-703 (1997). [CrossRef]
- R. Eckardt, Y. Fan, R. Byer, R. Route, R. Feigeison, and J. Laan, "Efficient second harmonic generation of 10- µm radiation in AgGaSe2," Appl. Phys. Lett. 47, 786-788 (1985). [CrossRef]
- P. B. Phua, B. S. Tan, R. F. Wu, K. S. Lai, L. Chia, and E. Lau, "High-average-power mid-infrared ZnGeP2 optical parametric oscillators with a wavelength-dependent polarization rotator," Opt. Lett. 31, 489-491 (2006). [CrossRef] [PubMed]
- Yu. M. Andreev, V. Yu. Baranov, V. G. Voevodin, P. P. Geiko, A. I. Bribenyukov, S. V. Izyumov, S. M. Kozochkin, V. D. Pis’mennyi, Yu. A. Satov, and A. P. Strel’tsov, "Efficient generation of the second harmonic of a nanosecond CO2 laser radiation pulse," Sov. J. Quantum Electron. 17, 1435-1436 (1987). [CrossRef]
- G. D. Boyd and F. G. Stortz, "Linear and nonlinear optical properties of ZnGeP2 and CdSe," Appl. Phys. Lett. 18, 301-303 (1971). [CrossRef]
- G. C. Bhar and G. C. Ghosh, "Temperature dependent phase-matched nonlinear optical devices using CdSe and ZnGeP2," IEEE J. Quantum Electron. 16, 838-843 (1980). [CrossRef]
- F. Madarasz, J. Dimmock, D. Dietz, and K. Bachmann, "Sellmeier paprameters for ZnGeP2 and GaP," J. Appl. Phys. 87, 1564-1565 (2000). [CrossRef]
- K. Kato, E. Takaoka, and N. Umemura, "New sellmeier and thermo-optic dispersion formulas for ZnGeP2," CLEO 2003, paper CtuM17.
- K. Kato, "Second-harmonic and sum-frequency generation in ZnGeP2," Appl. Opt. 36, 2506-2510 (1997). [CrossRef] [PubMed]
- S. Das, G. Bhar, S. Gangopadhyay, and C. Ghosh, "Linear and nonlinear optical properties of ZngeP2 crystal for infrared laser device applications: revisited," Appl. Opt. 42, 4335-4340 (2003). [CrossRef] [PubMed]
- D. E. Zelmon, E. A. Hanning, and P. G. Schunemann, "Refractive-index measurements and Sellmeier coefficients for zinc germanium phosphide form 2 to 9 µm with implications for phase matching in optical frequency-conversion devices," J. Opt. Soc. Am. B 18, 1307-1310 (2001). [CrossRef]
- W. Shi, Y. J. Ding, and P. G. Schunemann, "Coherent terahertz waves based on difference-frequency generation in an annealed zinc-germanium phosphide crystal: improvements on tuning ranges and peak powers," Opt. Commun. 233, 183-189 (2004). [CrossRef]
- G. C. Bhar, L. K. Samanta, D. K. Ghosh, and S. Das, "Tunable parametric ZnGeP2 crystal oscillator," Sov. J. Quantum Electron. 17, 860-861 (1987). [CrossRef]
- V. G. Dmitriviev, G. G. Gurzadyan, and D. N. Nikogosyan, Handbook of Nonlinear Optical Crystals (Springer, New York, 1997), p. 50.
- X. Mu and Y. J. Ding, "Optical-parametric generation and oscillation in periodically-poled lithium niobate in the presence of strong two-photon absorption," Opt. Commun. 242, 305-312 (2004). [CrossRef]

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