• E2M - 전기 전자와 첨단 소재
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• 제11권11호
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• pp.28-36
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• 1998

Widely tunable diodes integrated with periodically sampled and chirped DBR(distributed Bragg reflector) and an EA(electroabsorption) modulator are analyzed dynamically using the improved largesinal time-domain model. The tuning characteristics of sampled- and chirped-grating DBR laser diodes are demonstrated theoretically. The results of the simulation agree well with those of the experiment. And the intensity-modulation properties of the laser diodes integrated with an EA modulator are calculated. It is shown that the external modulation has the lower frequency chirp by 1/20 for the same extinction ratio than the direct modulation, and also the short pulse train can be generated using the optical gating of an EA modulator.

• 센서학회지
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• 제29권6호
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• pp.412-419
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• 2020

In this study, a PID control method for sweeping automatic linearization of a wavelength swept laser is proposed. First, the closedloop transfer function embodying the PID control is derived. Through the simulation of the function, K_p = 0.022, K_i = 0.008, K_d = 0.002 were obtained as the best PID coefficients for fast linear sweeping. The performance test using the PID coefficients showed that linear sweeping was held up well with a 98.7% decrement in nonlinearity after the 10th feedback, and 45 nm sweeping range, 1 kHz sweeping frequency, and 8.8 mW average optical power were obtained. The equipment consists of a fiber Bragg grating array, an optical-electronic conversion circuit, and a LabVIEW FPGA program. Every 5s, automatic feedback and PID control generate a new compensated waveform and produce a better linear sweeping than before. Compared with nonlinear sweeping, linear sweeping can reduce the cumbersome and time-consuming recalibration processes and produce more accurate measurement results.

• 한국광학회지
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• 제5권1호
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• pp.100-105
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• 1994

Littrow형 회절격자를 이용한 확장공진기를 657 nm 영역에서 연속동작하는 상용 InGaAsP 단일모우드 가시광 반도체를 이용하여 구성하였다. 제작한 확장공진기 시스템에서 657 nm InGaAsP 가시광 반도체 레이저의 선폭은 60 MHz에서 10 MHz 이하로 축소되었다. Littrow 회절격자의 설치각도와 레이저의 온도 및 주입 전류에 대한 반도체레이저의 주파수(파장) 의존성을 레이저 파장계를 이용하여 측정하였다. 상용 CQL820D 가시광 반도체레이저의 회절격자의 설치각도, 레이저 온도 및 주입전류에 대한 비례계수는 각각 1THz/mrad, 32.4 GHz/K, 그리고 6.14 GHz/mA 이었다.

• 한국소프트웨어감정평가학회 논문지
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• 제15권1호
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• pp.71-78
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• 2019

광대역 광통신 시스템에 사용되는 레이저는 우수한 주파수 선택성과 모드 안정성을 가져야한다. DFB(Distributed Feedback) 레이저는 고주파로 전류 변조를 하더라도 발진 주파수의 변화가 적다. 본 연구에서는 무반사 코팅을 하지 않은, 두 거울 면을 가진 1.55um의 파장을 갖는 DFB 레이저에서 이득 격자와 굴절률 격자가 동시에 존재할 때, 시뮬레이션 소프트웨어를 개발하여 종 방향으로의 발진 모드의 빔 분포를 해석하였다. 굴절률 격자와 이득 격자가 거울 면에서 갖는 위상 값의 변화에 따라서 DFB 레이저의 발진 모드에 대한 빔 분포 |R(z)|와 |S(z)|, 그리고 방사전력비 P_l/P_r를 비교 검증하였다. 거울 면에서의 격자 위상에 관계없이 발진 모드의 문턱 전류를 낮추고 주파수 안정성을 높이기 위해서는, κL이 8보다 커야한다.

• Journal of the Optical Society of Korea
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• 제13권1호
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• pp.53-59
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• 2009

A chirped-pulse amplification Ti:sapphire laser system has been designed using a 10-Hz 100-TW Ti:sapphire laser to generate 0.1-Hz 0.5-PW laser pulses and optimize their temporal qualities such as temporal contrast and pulse duration. A high-energy booster amplifier to be added is expected to produce an energy above 30 J through the parasitic lasing suppression and the efficient amplification. To improve the temporal contrast of the laser pulses, a high-contrast 1-kHz amplifier system is used as a front-end. A grating stretcher which makes the laser pulse have 1-ns duration is used to prevent optical damages due to high pulse energy during amplification. A grating compressor has been designed with group delay analysis to obtain the recompressed pulse duration close to the transform-limited pulse duration. The final laser pulses are expected to have energy above 20 J and duration below 40 fs.

• 한국정보통신학회논문지
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• 제20권1호
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• pp.161-166
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• 2016

본 논문에서는 광섬유 브래그 격자의 공정조건 변화에 따른 $Co^{60}$ 감마방사선 영향을 연구하였다. 광섬유 브래그 격자는 붕소가 첨가된 광민감 광섬유를 이용하여 UV KrF 레이저 세기를 달리하여 제작하였으며, 제작된 광섬유 브래그 격자 센서에 총 선량 33.8 kGy 감마선을 조사하였다. 실험결과를 통하여, 격자 공정을 위한 UV 레이저 세기가 광섬유 브래그 격자의 방사선 민감도에 큰 영향을 줄 수 있다는 것을 확인하였으며, 레이저 공정조건 변화에 따른 방사선에 의한 광섬유 브래그 파장의 변화는 30 % 이상의 차이를 보였다.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2000년도 춘계학술대회논문집A
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• pp.415-419
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• 2000

Multi-degree-of-freedom (MDOF) displacement measurement Is needed In many application fields: precision machine control, precision assembly, vibration analysis, and so on. This paper presents a new MDOF displacement measurement method using a laser diode (LD), two position-sensitive detectors (PSDs), and a conventional diffraction grating. It utilizes typical features of a diffraction grating to obtain the information of MDOF displacement. MDOF displacement is calculated from the independent coordinate values of the diffracted ray spots on the PSDs. Forward and inverse kinematic problems were solved to compute the MDOF displacement of a rigid body. Experimental results show maximum absolute errors of less than ${\pm}10$ micrometers in translation and ${\pm}30$ arcsecs in rotation.

• ETRI Journal
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• 제28권5호
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• pp.545-554
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• 2006

A widely tunable multi-channel grating cavity laser is proposed and experimentally demonstrated. The device is implemented in Littman configuration with an echelle grating based on Rowland circle construction and realized by monolithically integrating all elements in an InP substrate. Lasing wavelength is selected by turning on an amplifier and the appropriate channel element in the array, and it is tuned by controlling light deflection electrically. The 6-channel device exhibits a tuning range of about 50 nm with a side mode suppression ratio of more than 30 dB. This is accomplished by adjusting the applied current of the dispersive element and phase control section.

• Transactions on Electrical and Electronic Materials
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• 제5권6호
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• pp.219-222
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• 2004

This paper discovers that there are some peculiar properties that can remove holography grating, which was made in chacogenide thin film by impressed voltage. The thin films were used are $As_{40}Ge_{10}Se_{15}S_{35}$, and we use He-Ne laser in order to form thin films. I-V curved line in a thin film before a lattice was made has the critical point, about 3.7 V. Moreover, the I-V curved line increased current intensity at over 4 V after it made thin film. In addition, while holography grating is being made, and when it has the highest diffraction efficiency, a lattice can be deleted if put more voltage into it.

• 한국전기전자재료학회논문지
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• 제16권8호
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• pp.736-739
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• 2003

We prepared the chalcogenide As$\_$40/Ge$\_$10/Se$\_$15/S$\_$35/, Se$\_$75/Ge$\_$25/ thin film. Holographic grating was formed by the He-Ne laser( λ =633 nm). Annealing at 100$^{\circ}C$ and 200$^{\circ}C$ has been used to change the optical property of chalcogenide thin films for holographic grating formation. As the results, large variation of the optical property was generated at the As$\_$40/Ge$\_$10/Se$\_$15/S$\_$35/ chalcogenide film. Diffraction efficiency of the As$\_$40/Ge$\_$10/Se$\_$15/S$\_$35/ film has been enhanced about three times