Optical Second Harmonic Generation in Form of Coherent Cerenkov Radiation From a Thin-Film Waveguide

Tien, P. K.; Ulrich, R.; Martin, R. J.

doi:10.1063/1.1653265

Cited by 255 publications

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“…This is somewhat analogous to the Cherenkovtype SHG in waveguides. 12 The SHG process can be optimized by adjusting the initial ͑tϭ0͒ index mismatch of the interacting waves at any particular input power level. Figure 5 shows such angular tuning curve for SHG.…”

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Nonlinear self-phase matching of optical second harmonic generation in lithium niobate

Orlov

Yariv

Segev

1996

Applied Physics Letters

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We show that the nonlinear index perturbation due to light-induced photovoltaic space-charge field in LiNbO 3 can give rise to self-phase matching of second harmonic generation. Increase of the conversion efficiency is accompanied by formation of stationary and nonstationary patterns in the spatial structure of the generated second harmonic. The space-charge field can be induced either by the initially non-phase-matched second harmonic or by an external seed. © 1996 American Institute of Physics. ͓S0003-6951͑96͒04412-9͔ Different techniques for phase matching the nonlinear interactions of optical beams have been developed including temperature and angular tuning for birefringent phase matching and quasiphase matching 1 using an alternating sign optical nonlinearity.Photorefraction ͓optical damage ͑Refs. 2 and 3͒ in LiNbO 3 ͔ is, in general, a negative feature for optical second harmonic generation ͑SHG͒ applications, since it locally modifies the birefringence of the crystal, thus, changing the phase-matching conditions for SHG dramatically. We demonstrate that the large nonlinear index perturbation due to photovoltaic effect can promote a new effect, namely, the self-phase matching of SHG ͑initially nonphase matched͒ which manifests itself in a large increase in conversion efficiency and pattern formation in the structure of the generated SH beam. 4 As an optical source, we employ a Q-switched ͑repeti-tion rate 1 kHz͒ mode-locked ͑50 MHz͒ Nd:YAG laser ͑ ϭ1.064 m͒, emitting 8 -10 mode-locked 100 ps pulses within the Q-switched envelope. We focus ͑Fig. 1, inset͒ the ordinarily polarized IR radiation with a 50 mm focal length lens on a lightly Fe-doped 2 mm thick LiNbO 3 crystal, the c axis of which is in the plane of incidence. The focal spot size of the infrared beam is ϳ70 m. The extraordinarily polarized second harmonic light ͑ϭ0.532 m͒ emerging from the far side of the crystal is captured by a charge coupled device ͑CCD͒ camera and its total cw power is measured with a photodetector.We observe that for relatively small angles of incidence ͑between 0°and approximately 20°͒ of the fundamental light the second harmonic signal increases with time ͑Fig. 1͒ by a factor ϳ100 from a few W to several mW average power ͑up to 0.1% in conversion efficiency͒. The large enhancement in the SH power is accompanied by a pattern formation in the spatial structure of the SH beam ͑Fig. 2͒. The SH beam first becomes elongated along the direction of the c axis of the crystal, has two distinct side lobes in the intermediate stage ͓Fig. 2͑b͔͒, and eventually settles into the pattern of Fig. 2͑c͒. At the same time, the ordinarily polarized infrared beam does not experience substantial phase distortion, as seen from its far-field pattern, which remains roughly a Gaussian. The enhancement in the SHG can also be induced by the green ͑ϭ0.532 m͒ seeding beam alone. If a spot previously exposed to the externally injected seeding SH light ͑focused with the same lens͒ is probed by the infrared light the initially ͑tϭ0͒ generated SH signal is...

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Nonlinear self-phase matching of optical second harmonic generation in lithium niobate

Orlov

Yariv

Segev

1996

Applied Physics Letters

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“…In a waveguide with a modal phase Photonics 2016, 3, 42 5 of 10 matching scheme, due to a faster frequency-dependent effective index in the THz range with respect to the mid-IR index (n mid-IR ), the modal phase matching is only satisfied within a relatively narrow frequency range for a certain waveguide [25]. In contrast to this narrow-band phase-matching scheme, theČerenkov scheme [26] has been used as an effective broad-band phase matching method for THz generation in the externally-pumped optical rectification or DFG setups [27].Čerenkov nonlinear emission occurs when the nonlinear polarization wave propagates at a higher phase velocity compared to that of the nonlinear radiation, as shown in Figure 4a. For THz DFG in QCLs, the waveguide forČerenkov phase matching scheme can be designed so that the THz refractive index (n THz ) in the QCL substrate is higher than the mid-IR group effective refractive index (n mid-IR ).…”

Section: Composite Dfb Waveguide and Epi-down čErenkov Phase Matchingmentioning

confidence: 99%

“…In contrast to this narrow-band phase-matching scheme, the Čerenkov scheme [26] has been used as an effective broad-band phase matching method for THz generation in the externally-pumped optical rectification or DFG setups [27]. Čerenkov nonlinear emission occurs when the nonlinear polarization wave propagates at a higher phase velocity compared to that of the nonlinear radiation, as shown in Figure 4a.…”

Section: Composite Dfb Waveguide and Epi-down čErenkov Phase Matchingmentioning

confidence: 99%

Recent Advances in Room Temperature, High-Power Terahertz Quantum Cascade Laser Sources Based on Difference-Frequency Generation

Razeghi

2016

Photonics

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We present the current status of high-performance, compact, THz sources based on intracavity nonlinear frequency generation in mid-infrared quantum cascade lasers. Significant performance improvements of our THz sources in the power and wall plug efficiency are achieved by systematic optimizing the device's active region, waveguide, and chip bonding strategy. High THz power up to 1.9 mW and 0.014 mW for pulsed mode and continuous wave operations at room temperature are demonstrated, respectively. Even higher power and efficiency are envisioned based on enhancements in outcoupling efficiency and mid-IR performance. Our compact THz device with high power and wide tuning range is highly suitable for imaging, sensing, spectroscopy, medical diagnosis, and many other applications.

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“…식 ( [10] , 이를 Cerenkov-idler configuration이라고 한 다. [4] 변수 변환             을 하면,    과    는 다음과 같이 다시 쓸 수 있다.…”

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Zero Cerenkov Radiation Angle Effect in Optical Parametric Amplification in the Cerenkov-idler Configuration

Suh¹

2014

Journal of the Institute of Electronics and Information Enginee

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평판 도파로에서 Cerenkov-idler configuration 형태의 광학적 매개증폭에 대해서 결합모드 이론을 적용하여 결합모드 방정 식을 유도하고, 이 방정식의 근사해를 펌핑광의 고갈(depletion)이 없는 경우에 대해서 구한다. 이 근사해로부터 발생되는 idler 의 체렌코프 복사각이 0°도에 접근할 때 signal의 이득이 크게 향상될 수 있음을 보여주고 수치적 예를 보인다. AbstractOptical parametric amplification has been analyzed for the Cerenkov-idler configuration in planar waveguides. The coupled-mode theory is employed for the analysis. The coupled-mode equations are derived and the approximate analytic solution is obtained for no pump depletion. From the analytic solution, it is shown that the signal power gain can be enhanced as the Cerenkov radiation angle of the idler approaches to zero. The numerical example is also shown for the effect of the Cerenkov radiation angle approaching zero.

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Optical Second Harmonic Generation in Form of Coherent Cerenkov Radiation From a Thin-Film Waveguide

Cited by 255 publications

References 4 publications

Nonlinear self-phase matching of optical second harmonic generation in lithium niobate

Nonlinear self-phase matching of optical second harmonic generation in lithium niobate

Recent Advances in Room Temperature, High-Power Terahertz Quantum Cascade Laser Sources Based on Difference-Frequency Generation

Zero Cerenkov Radiation Angle Effect in Optical Parametric Amplification in the Cerenkov-idler Configuration

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