• Journal of the Optical Society of Korea
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• v.8 no.4
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• pp.163-167
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• 2004

We propose and demonstrate an external optical modulation method based on TE/TM-mode absorption nulls in a Multiple Quantum Well(MQW) Fabry-Perot laser diode(FP-LD). The center wavelength of the absorption nulls is rapidly shifted to short-wavelength by the small current change(~1mA) in the FP-LD, which can modulate an optical signal with more than 10 dB of extinction ratio(ER). The shift of the center wavelength comes from the refractive index change due to anomalous dispersion and the plasma effect in MQW FP-LD waveguide. Non-inverting and inverting signals are made by TE- and TM-mode absorption nulls at 155.52 Mbps and BERs for the signals are measured.

• 제어로봇시스템학회:학술대회논문집
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• 1993.10b
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• pp.434-439
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• 1993

Described is a stabilizing circuit of the Doppler beat signal obtained by the coherence-dependent fiber-optic laser Doppler velocimeter (LDV), which employs both a self-mixing laser diode (SM-LD) and a 10m-100m long optical fiber. The stabilizing circuit maintains the SM-LD drive current at an optimum value, which gives a maximum Doppler signal during long hours.

• Korean Journal of Optics and Photonics
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• v.14 no.3
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• pp.327-330
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• 2003

We present the fabrication and measured performance of a wavelength tunable Butt coupled DBR-LD. An average coupling efficiency between active layer and passive waveguide layer was measured over 85％per facet, and the average threshold current was 21 ㎃ for the waveguide integrated DBR laser. High output power of Butt coupled DBR-LD was obtained over 25 ㎽. As high as 25 ㎽ of output power was achieved by the butt coupled method. The maximum wavelength tuning range is about 7.4 nm, and the side mode suppression ratio was more than 40 ㏈ using 1.3 ${\mu}{\textrm}{m}$ InGaAsP waveguide layer.

• ETRI Journal
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• v.45 no.2
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• pp.193-202
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• 2023

We demonstrate the transmission of uncompressed 4K videos over the photonics-based terahertz (THz) wireless link using a directly modulated distributed feedback laser diode (DFB-LD). For optical heterodyne mixing and data modulation, a DFB-LD was employed and directly modulated with a 5.94-Gb/s non-return-to-zero signal, which is related to a 6G-serial digital interface standard to support ultra-high-definition video resolution. We derived the optimal frequency of the THz carrier by varying the wavelength difference between DFB-LD output and Tunable LD output in the THz signal transmitter to obtain the best transmission performances of the uncompressed 4K video signals. Furthermore, we exploited the negative laser-to-filter detuning for the adiabatic chirp management of the DFB-LD by the intentional discrepancy between the center wavelength of the optical band-pass filter and the output wavelength of the DFB-LD. With the help of the abovementioned methods, we successfully transmitted uncompressed 4K video signals over the 2.3-m wireless transmission distance without black frames induced by time synchronization error.

• Electrical & Electronic Materials
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• v.13 no.1
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• pp.11-18
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• 2000

최근 10여년 사이에 III-nitride 화합물 반도체가 전 세계적으로 주목을 받고 있다. 이는 질화물의 조성에 따라 자외선 영역에서 가시 광선의 전 파장, 측 자색에서 적색 영역대의 광소자 및 고온 고출력 전자소자에 쓰일 수 있기 때문이다. 지금까지 고휘도의 청색, 녹색 LED(Light Emitting Diode)는 상용화되어 있어, UC LD(Ultra-Violet Laser Diode)는 10,000 시간 상온 연속 발진에 성공하여 상용화의 단계에 이르고 있다. 그러나 많은 연구 투입에 비례하여 얻어지는 결과물의 효율은 그리 높지 않은 분야로 LED를 수준 급으로 상용화하는 곳은 세계에서 5개정도로 국한되면, 그 기술이 전파됨이 그리 쉽지 않다. LD(laser Diode)의 경우 상용화 초기 단계로 보편적 신뢰성을 확보하기까지는 또 다른 breakthrough 확보가 필요하며, 궁극적인 기술 전개는 기판을 해결하는 것에서 올 수 있다. 본 논문에서는 이러한 III-nitride 반도체 소자 개발을 가능하게 한 MOCVD(Metaloganic Chemical Vapor Deposition) 결정 성장 방법과, 기존에 사용화 되어 있는 LED 소자 특성 및 국내외 개발 동향 및 향후 발전 방향을 소개하고자 한다.

• Proceedings of the KWS Conference
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• 2002.10a
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• pp.561-569
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• 2002

Laser has been called a "Quantum Machine" because of its mechanism of generation since the development on July 7,1960.by T.H.Maiman. We can now use this machine as a tool for manufacturing in industries. At present, 45kW CO2 laser, 10kW Nd:YAG laser, 6kW LD pumped YAG laser and 4kW direct diode laser facilities are available for welding a heavy steel plate of 40mm in thickness and for cutting metals at high speed of 140m/min. Laser Materials Processing is no longer a scientific curiosity but a modern tool in industries. Lasers in manufacturing sector are currently used in welding, cutting, drilling, cladding, marking, cleaning, micro-machining and forming. Recently, high power laser diode, 10kW LD pumped YAG laser, 700W fiber laser and excimer laser have been developed in the industrialized countries. As a result of large numbers of research and developments, the modem laser materials processing has been realized and used in all kinds of industries now. In the present paper, metallurgical studies on laser materials processing such as porosity formation, hot cracking and the joint performances of steels and aluminum alloys and dissimilar joint are discussed after the introduction of laser facilities and laser applications in industries such as automotive industry, electronics industry, and steel making industry. The wave towards the use of laser materials processing and its penetration into many industries has started in many countries now. Especially, development of high power/quality diode laser will be accelerate the introduction of this magnificent tool, because of the high efficiency of about 50%, long life time and compact.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.17 no.4
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• pp.8-12
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• 2003

Characteristics of optical transceiver module in radio frequency(RF) band were investigated with TO-can packaged Fabry-Perot laser diode(FP-LD). R-L-C parameters for equivalent circuit model of the LD were extracted with an impedance analyzer. With this model, impedance matching to the packaged LD could be performed by eliminating inductive components of the leads in the package by using lumped chip capacitors that have opposite reactance, while it shows resonance dip in low frequency band. The resonance dip could be removed using lumped elements for impedance matching by shifting the resonance frequency to the region out of interest.

• Transactions of the Society of Information Storage Systems
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• v.2 no.1
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• pp.21-25
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• 2006

The new multimedia information environment requires smaller optical data storage systems. However, one of the difficulties encountered in designing small form factor(SFF) optical pick-up is to emit the heat which is generated from laser diode(LD). Heat generated at the LD can reduce the optical performance of the system and the lifetime of LD. Therefore, it is important to include the thermal design in the design stage of SFF optical pick-up system for high performance and the longer lifetime of LD, and furthermore, to analyze the thermal characteristics of LD in detail micro heat transfer analysis is necessary. In the present study, micro heat transfer analysis was performed using the finite element method for the $28{\times}11{\times}2mm^3$ super slim swing-arm type optical pick-up actuator for Blu-ray disk. Two different materials were used for a swing-arm; a double layer polycarbonate/steel structure and a single aluminum structure.

• Proceedings of the Optical Society of Korea Conference
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• 1990.02a
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• pp.69-72
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• 1990

For the effective heat transfering in Lser Diodes, Beam-Lead structure were introduced which is applicable to hybrid Optoelectronic Integrated Circuits. A 5-layer planar structure Laser Diode is fabricated and Beam-Lead is made by Au plating. And carrier was made by etching Si substrate and LD was mounted on a carrier. The thermal resistance was measured and we could certain that Beam-Lead structure behaves well as a heat sink.

• Proceedings of the Optical Society of Korea Conference
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• 2001.02a
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• pp.48-49
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• 2001

GaN는 wurzite structure를 갖는 wide bandgap III-V족 반도체로서, 청색 반도체 laser diode (LD), light emitting diode (LED)등으로 응용되는 물질이다. InGaN quantum well은 GaN계의 청색 LD, LED 구조에서 활성층으로 사용되기 때문에 이에 대한 광학적 연구가 활발하다. InGaN는 GaN위에 성장하면 strain에 의해 piezoelectric 효과가 크게 나타나는 것으로 알려져 있다. 이러한 piezoelectric potential에 의해 외부에서 voltage가 가해지지 않은 상황에서도 InGaN quantum well내의 electron, hole의 wave function이 비대칭 potential의 영향을 받게된다. (중략)