• Journal of the Optical Society of Korea
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• 제12권3호
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• pp.205-209
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• 2008

We demonstrated a simple way of evaluating the duty cycle error in periodically polled lithium niobate(PPLN) based on the method of binary phase diffraction grating. To demonstrate this method, -Z face etched PPLN of desired periods were fabricated by the standard electric field poling technique. The etched PPLN was considered as a surface-relief binary phase grating. The diffraction patterns were recorded for different spatial locations along the length of the sample. The experimentally observed efficiencies of the diffracted orders were compared with the theoretically calculated values to estimate the duty cycle error.

• Journal of the Optical Society of Korea
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• 제14권4호
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• pp.420-423
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• 2010

We fabricated 1 mm-thick periodically-poled lithium niobate (PPLN) crystals by using a high-voltage amplifier for standard electric field poling combined with a voltage multiplier. Furthermore, two 1 mm-thick PPLNs were directly bonded to make a 2 mm-thick PPLN. The large aperture allowed broad angular tuning, and a broad spectral range of quasi-phase matched second-harmonic generation can be achieved in a single channel. High-power applications are also expected.

• Journal of the Optical Society of Korea
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• 제18권6호
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• pp.762-765
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• 2014

We fabricated a periodically poled lithium niobate (PPLN) by direct laser-writing of a quasi-phase-matching (QPM) structure in photolithographic process. Because we do not need to prepare a photomask by electron-beam writing, the "maskless" process shortens the fabrication time and significantly reduces the cost. We evaluated the poling quality of the direct laser-written PPLN by measuring the diffraction noise from the surface relief pattern of the fabricated QPM grating and comparing the results to those from a conventional PPLN made with a photomask. The quality of the PPLN fabricated by direct laser-writing was shown to be equivalent to that fabricated by the conventional method.

• Current Optics and Photonics
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• 제4권1호
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• pp.63-68
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• 2020

We built an optical parametric oscillator (OPO) generating orthogonally polarized signals at different wavelengths simultaneously, based on a periodically poled lithium niobate (PPLN) crystal. The OPO was pumped by ns-pulses at 1.064 ㎛ from a diode-pumped solid-state laser, where we found the type-0 and the type-1 quasi-phase matching conditions were satisfied simultaneously in the PPLN crystal. This enabled us to create a coherent light source which can emit dual signals which could be accessed easily by rotating a polarizer.

• 한국광학회:학술대회논문집
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• 한국광학회 1999년도 제16회 광학 및 양자전자 학술발표회Proceedings of 16th Optics and Quantum Electronics Conference, 1999
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• pp.66-67
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• 1999

• Journal of the Optical Society of Korea
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• 제5권4호
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• pp.136-139
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• 2001

We investigated a high-output ower, periodically poled lithium niobate(PPLN) optical parametric oscillator(OPO) pumped by a Q-switched Nd:YAG laser. Given the low optical damage threshold and the limited aperture (0.5mm thick) of PPLN, we tried to maximize the signal output power in a linear cavity consisting of two flat mirrors with a loosely focused pump beam. It is found that this simple cavity structure allowed a robust OPO operation, which was not sensitive to alignment compared with the conventional ones using concave mirrors. A maximum energy of 100$\mu$J/pulse was achieved for the signal at 1.36${\mu}{\textrm}{m}$, while the oscillation threshold was 0.3 mJ/pulse for the pump at 1064 nm.

• 한국광학회:학술대회논문집
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• 한국광학회 2005년도 하계학술발표회
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• pp.262-263
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• 2005

• 한국광학회지
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• 제32권2호
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• pp.62-67
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• 2021

본 연구에서는 모드 잠금된 ps-펄스 광섬유 레이저와 연속 발진하는 좁은 선폭의 반도체 레이저를 이용하여 주기적 분극반전된 LiNbO3(periodically poled lithium niobate; PPLN) 결정에서 합주파수 생성 연구를 수행하였다. 모드 잠금된 펄스 레이저는 중심 파장이 1560.7 nm이고 스펙트럼의 폭은 약 1.1 nm이며, 연속 발진 반도체 레이저는 중심 파장이 1551 nm이고 스펙트럼의 폭은 약 6 MHz로 동작한다. 합주파수 생성을 효과적으로 수행하기 위해서 하나의 단일 모드 광섬유를 이용하여 PPLN 결정 내부에서 두 펌프 광원을 공간적으로 완전히 중첩하였다. 모드 잠금된 펄스 레이저와 좁은 선폭의 연속발진 반도체 레이저에 의해서 모드 잠금된 펄스 형태의 778 nm인 합주파수 생성을 스펙트럼과 시간적인 변화로 확인하였다. 본 연구 결과는 주파수 제어가 가능한 광주파수 빗(optical frequency comb)을 이용한 광주파수 측정 및 고분해 레이저 분광 연구 등 다양하게 응용될 수 있을 것으로 기대된다.

• Journal of the Optical Society of Korea
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• 제15권2호
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• pp.182-186
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• 2011

A poling method using multiple negative voltage was introduced to fabricate periodically poled lithium niobate (PPLN) devices with quasi-phase matching (QPM) period of $12.9\;{\mu}m$ by utilizing an real-time visualization system. We also performed variation of the electric field during the poling. Two different conventionally used poling method, negative and positive single pulses, were used and the poling quality compared through microscopic images and far-field diffraction pattern analysis. Etched images on the +z and -z surfaces of PPLN showed that negative multiple pulse poling presented the highest periodicity in domain structures among the three methods. Duty ratio and its standard deviation were measured by analyzing far-field diffraction patterns. The newly introduced method of negative multiple pulse poling had duty ratio of 0.42 which was close to the ideal value of 0.50 and standard deviation of 0.020 that was about 3 times smaller than that of the other conventional methods.

• 한국광학회지
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• 제16권4호
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• pp.366-375
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• 2005

Ti 확산 리튬나오베이트 채널 광도파로의 z-축 분극을 주기적으로 $180^{\circ}$ 위상 변화시키는 Ti:PPLN 제작 공정을 검토하고, 개선하였다. 분극반전 공정에 적합한 지그와 Labview 프로그램을 이용하여 전하량 제어시스템을 고안하였다. 분극반전에 필요한 전하량으로부터 분극에 적절한 고전압 펄스와 duty-cycle을 조절하였으며, 분극에 필요한 임계 전압 보다 작은 전압을 인가한 상태에서 누설전류의 변화를 관찰하여 절연파괴 현상을 또한 최소화하였다.