• 대한전자공학회논문지SD
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• 제41권4호
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• pp.41-47
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• 2004

본 논문에서는 마이크로파 feedline을 포함하고, 광도파관과 마이크로파 feedline간의 임피던스 부정합을 고려하여 전계 흡수광변조기(traveling-wave electro-absorption modulator, TW-EAM)의 마이크로파 특성을 분석하였다. Co-planar waveguide(CPW)와 microstrip의 하이브리드 구조를 가지는 광도파관 부분은 등가회로를 통해 모델링 하였으며, 등가회로의 인덕턴스(L)와 커패시턴스 (C)는 3차원 FDTD를 기반으로 한 수식화를 통하여 구하였다. CPW 구조의 마이크로파 feedline은 모멘텀방식을 이용해 분석하였다. 이와 같은 분석을 통해 TW-EAM의 특성을 보다 정확하게 분석 할 수 있음을 제시한다.

• 한국정보통신설비학회:학술대회논문집
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• 한국정보통신설비학회 2003년도 하계학술대회
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• pp.172-174
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• 2003

In this paper, we analyze the traveling-wave electro-absorption modulator (TW-EAM) in consideration of the microwave feed-line. The TW-EAM is analyzed by using the equivalent circuit model. The microwave feed-line isanalyzed by momentum method. In a view point of microwave characteristics, we present the effect of the structure and the length of microwave feed-line.

• 한국광학회:학술대회논문집
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• 한국광학회 2000년도 제11회 정기총회 및 00년 동계학술발표회 논문집
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• pp.270-271
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• 2000

Among many optical modulators, we are interested in traveling-wave(TW) multiple quantum well(MQW) electro-absorption modulator which can be used for wide-band applications, covering DC to 30GHz or higher frequencies. In this study, we simulate a 1.3mm InGaAs/lnGaAsP TW MQW EAM using the 3D Finite Difference-Time Domain (FDTD) method. We identify that several geometric factors affect Microwave charateristics. Our calculated data provide useful information to optimize and fabricate ridge-type TW CPW EAM.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2012년도 제43회 하계 정기 학술대회 초록집
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• pp.319-320
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• 2012

Large aperture optical modulator called optical shutter is a key component to realize time-of-flight (TOF) based three dimensional (3D) imaging systems [1-2]. The transmission type electro-absorption modulator (EAM) is a prime candidate for 3D imaging systems due to its advantages such as small size, high modulation performance [3], and ease of forming two dimensional (2D) array over large area [4]. In order to use the EAM for 3D imaging systems, it is crucial to remove GaAs substrate over large area so as to obtain high uniformity modulation performance at 850 nm. In this study, we propose and experimentally demonstrate techniques for backside etching of GaAs substrate over a large area having high uniformity. Various methods such as lapping and polishing, dry etching for anisotropic etching, and wet etching ([20%] C6H8O7 : H2O2 = 5:1) for high selectivity backside etching [5] are employed. A high transmittance of 80% over the large aperture area ($5{\times}5mm^2$) can be obtained with good uniformity through optimized backside etching method. These results reveal that the proposed methods for backside etching can etch the substrate over a large area with high uniformity, and the EAM fabricated by using backside etching method is an excellent candidate as optical shutter for 3D imaging systems.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2013년도 제45회 하계 정기학술대회 초록집
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• pp.220-220
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• 2013

Surface-normal transmission electro-absorption modulator (EAM) are attractive for high-definition (HD) three-dimensional (3D) imaging application due to its features such as small system volume and simple epitaxial structure [1,2]. However, EAM in order to be used for HD 3D imaging system requires uniform modulation performance over large area. To achieve highly uniform modulation performance of EAM at the operating wavelength of 850 nm, it is extremely important to remove the GaAs substrate over large area since GaAs material has high absorption coefficient below 870 nm which corresponds to band-edge energy of GaAs (1.424 eV). In this study, we propose and experimentally demonstrate a transmission EAM in which highly selective backside etching methods which include lapping, dry etching and wet etching is carried out to remove the GaAs substrate for achieving highly uniform modulation performance. First, lapping process on GaAs substrate was carried out for different lapping speeds (5 rpm, 7 rpm, 10 rpm) and the thickness was measured over different areas of surface. For a lapping speed of 5 rpm, a highly uniform surface over a large area ($2{\times}1\;mm^2$) was obtained. Second, optimization of inductive coupled plasma-reactive ion etching (ICP-RIE) was carried out to achieve anisotropy and high etch rate. The dry etching carried out using a gas mixture of SiCl4 and Ar, each having a flow rate of 10 sccm and 40 sccm, respectively with an RF power of 50 W, ICP power of 400 W and chamber pressure of 2 mTorr was the optimum etching condition. Last, the rest of GaAs substrate was successfully removed by highly selective backside wet etching with pH adjusted solution of citric acid and hydrogen peroxide. Citric acid/hydrogen peroxide etching solution having a volume ratio of 5:1 was the best etching condition which provides not only high selectivity of 235:1 between GaAs and AlAs but also good etching profile [3]. The fabricated transmission EAM array have an amplitude modulation of more than 50% at the bias voltage of -9 V and maintains high uniformity of >90% over large area ($2{\times}1\;mm^2$). These results show that the fabricated transmission EAM with substrate removed is an excellent candidate to be used as an optical shutter for HD 3D imaging application.

• 한국정보통신학회논문지
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• 제17권8호
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• pp.1968-1973
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• 2013

전계 흡수 변조기가 집적된 이중 전극 분포 궤환형 레이저를 사용하여 광신호의 변조 응답 향상을 실현하였다. 이 중 전극 구조의 분포 궤환형 반도체 레이저는 자려 펄스 발진 현상으로 인해 수 기가 헤르쯔의 모드 간격을 가진 다중 광모드 발진 현상을 보인다. 이 현상을 이용하여 RF 신호에 대한 광원의 변조 특성을 6 GHz 변조 신호에 대하여 약 20 dB 향상 시켰으며, 이러한 변조 성능 향상에 대하여 7 GHz의 주파수 가변 영역을 얻었다.

• Journal of the Optical Society of Korea
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• 제19권4호
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• pp.371-375
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• 2015

The impact of equivalent optical bandwidth on the performance of a system using a reflective electroabsorption modulator (R-EAM) based optical source has been experimentally evaluated with signals operating at 2.5 Gb/s and beyond. The equivalent optical bandwidth of our source with a broadband seed light was simply adjusted by using a bandwidth tunable optical filter. From the measurements, we have estimated the required equivalent optical bandwidth of our source for an error-free transmission (@ bit-error-rate of $10^{-12}$) and a forward error correction (FEC) threshold of $2{\times}10^{-4}$.

• ETRI Journal
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• 제28권4호
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• pp.533-536
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• 2006

A distributed Bragg reflector (DBR) laser and a high speed electroabsorption modulator (EAM) are integrated on the basis of the selective area growth technique. The typical threshold current is 4 to 6 mA, and the side mode suppression ratio is over 40 dB with single mode operation at 1550 nm. The DBR laser exhibits 2.5 to 3.3 mW fiber output power at a laser gain current of 100 mA, and a modulator bias voltage of 0 V. The 3 dB bandwidth is 13 GHz. A 10 Gbps non-return to zero operation with 12 dB extinction ratio is obtained. A four-channel laser array with 100 GHz wavelength spacing was fabricated and its operation at the designed wavelength was confirmed.

• 대한전자공학회논문지TC
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• 제42권12호
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• pp.53-62
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• 2005

본 논문은 휴대인터넷시스템의 수동피코셀 제안과 엑세스포인트와 수동형 피코셀간의 Radio over Fiber(ROF)접속 구도에 대한 것이다. 휴대인터넷시스템(Wibro)은 시속 60km의 중속도의 이동 단말에 50Mbps의 IP 기반 데이터서비스를 제공하는 것이다. 따라서, 서비스를 제공하기 위하여 초기에 셀의 구축비용을 최소화 하는 것이 요구된다. 본 논문은 이러한 요구사항을 만족하는 수동형 피코셀을 제안하고 이의 접속구도에 대하여 제안한 것이다. 기존의 Fabry-Perot(FP) 레이저를 채용하는 ROF 링크의 특성과 수동형Electro-absorption Modulator(EAM)를 이용한 수동형 피코셀의 특성을 측정하여 Wibro시스템에 이의 접속 가능성을 보이고 수동형피코셀의 RF 커버리지를 해석하여 가능성을 검증하였다.

• 대한전자공학회논문지TC
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• 제43권9호
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• pp.158-164
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• 2006

WLAN 및 이동통신은 계속해서 많은 서로 다른 표준으로 진화함에 따라 이동통신 사업자는 기술적 경제적 많은 어려움에 직면하고 있다. 따라서 끊임없는 시스템 업그레이드가 필요하게 된다. 이러한 문제를 해결하기 위한 새로운 접근 방법을 모색하여 그 타당성을 연구하였다. 즉, electro-absorption modulator(EAM) 과 optical single sideband (OSSB)에 기반한 radio over fiber (RoF) 기술을 사용해 저가, 단순, 주파수변화 및 프로토콜 변화가 없는 트랜스패런트한 무선 액세스 망을 구축하여 그 해결책을 제시하였다. 본 논문에서는 프로토타입 CATV 용 60GHz 대 무선 RoF 분배시스템을 구축하여 broadband convergence network (BcN)의 무선 액세스망에 사용가능성을 타진하였다.