• Korean Journal of Optics and Photonics
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• v.22 no.2
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• pp.102-107
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• 2011

In this paper, a small double ring resonator reflector was designed and fabricated using a polymer waveguide, and the measurement result was discussed. A widely tunable characteristic of the small double ring resonator caused by the Vernier effect, which results from the difference of the ring radii, was observed. The insertion loss of the double ring reflector was reduced by minimizing the device length to be as short as possible, and thus the output power and the SMSR (side mode suppression ratio) was greatly enhanced. The hybrid integrated laser based on the small double ring resonator reflector lased with the SMSR of 45 dB. In addition, the wide tuning range of 40 nm could be obtained by injecting a current of 30 mA to an electrode on top of the reflector.

• Korean Journal of Optics and Photonics
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• v.14 no.3
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• pp.321-326
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• 2003

We constructed grating- tuned external cavity semiconductor lasers using Littman and Littrow configuration, for which the wavelengths are tuned by rotation of the grating. This wavelength tunable semiconductor laser is one of the main devices of WDM optical communication. In Littman configuration, the wavelength range of about 60 nm (The C- and L-band range of 1,530~1,590 nm) was obtained by changing the incidence angle of the grating about $\pm$1$^{\circ}$ from the incidence angle of 70$^{\circ}$. In the 40 nm tuning range, the output power variation was less than 1.25 ㏈ and the side mode suppression ratio(SMSR) was 32 ㏈. In Littrow configuration (The incidence angle and the first order diffraction angle is the same, i.e. $\alpha$=$\delta$), the wavelength tuning range was about 80 nm for the same conditions used in Littman configuration except the incidence angle ($\alpha$=49$^{\circ}$). In 60 nm tuning range, the output power variation was less than 1.5 ㏈ and SMSR was 35 ㏈.

• Journal of KIISE:Information Networking
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• v.29 no.2
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• pp.129-140
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• 2002

In this paper, we consider the problem of packet transmission in a wavelength division multiplexed(WDM) optical network. Our network model assumes that receivers are fixed-tuned and transmitters are tunable such that optical lasers assigned to transmitters have limited access to the network bandwidth: hence each node must be equipped with multiple optical lasers and/or multiple optical filters in order to maintain a single-hop network. We first analyze scheduling all-to-all packet transmissions and present optimum scheduling for all-to-all packet transmissions. We then extend the analysis to the case of arbitrary traffic demands. We show that the scheduling with arbitrary traffic demand is NP-hard. A heuristic algorithm based on list scheduling is presented. The upper bound so obtained is compared with the lower bound and provides performance guarantees with arbitrary demands. The result are applicable to arbitrary tuning delay, arbitrary number of wavelength channels and optical lasers of arbitrary tuning ranges.

• Journal of Sensor Science and Technology
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• v.20 no.1
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• pp.46-52
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• 2011

In this paper, the swept source-optical coherence tomography system using frequency domain mode locked(FDML) laser has realized. The FDML swept source laser showed 55.03 kHz sweeping speed, 125 nm sweeping range, and 9 mW output optical power, which are the superiority of FDML laser compared to previous swept source lasers. Also, through the cross-sectional image captured at 5 frames per second for a mirror, a 1 mm-thickness glass plate, and a thumb bottom, the performance of the system has demonstrated.

• Ceramist
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• v.21 no.2
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• pp.59-74
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• 2018

Imaging in the Short Wave Infrared (SWIR) provides several advantages over the visible and near-infrared regions: enhanced image resolution in in foggy or dusty environments, deep tissue penetration, surveillance capabilities with eye-safe lasers, assessment of food quality and safety. Commercially available SWIR imagers are fabricated by integrating expensive epitaxial grown III-V compound semiconductor sensors with Si-based readout integrated circuits(ROIC) by indium bump bonding Infrared image sensors made of solution-processed quantum dots have recently emerged as candidates for next-generation SWIR imagers. They combine ease of processing, tunable optoelectronic properties, facile integration with Si-based ROIC and good performance. Here, we review recent research and development trends of various application fields of SWIR image sensors and nano-materials capable of absorption and emission of SWIR band. With SWIR sensible nano-materials, new type of SWIR image sensor can replace current high price SWIR imagers.

• Journal of the Optical Society of Korea
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• v.7 no.2
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• pp.97-101
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• 2003

The transmission characteristics of multi-channel long period fiber gratings (LPFGs) in terms of the physical parameters like the separation distance, grating length and number of gratings will be discussed. Their transmission characteristics such as channel spacing, number of channels, loss peak depth, and channel bandwidth can be easily controlled by physical parameters. Based on the experimental results, their applications to optical multiwavelength Raman lasers and optical sensors will be investigated. A multiwavelength Raman fiber ring laser with 9 WDM channels with 100 ㎓ spacing and 19 channels with 50 ㎓ spacing using tunable multi-channel LPFGs will be experimentally demonstrated. The fiber-optic sensing applications with high resolution and sensitivity based on multi-channel LPFGs will be also presented.

• Journal of Advanced Marine Engineering and Technology
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• v.33 no.8
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• pp.1220-1225
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• 2009

In this paper, a tunable fiber feedback laser based on the use of Sagnac loop filter and fiber Bragg grating (FBG) is proposed. The Sagnac loop filter using a high birefringence fiber provides precise 0.33-nm channel spacing as a multi-wavelength grid filter. Ni-Cr wire wound on the FBG is useful to induce the thermo-optic effect of the fiber. Two types of FBG structures, which have a different length of wire, are demonstrated to show the wavelength shift and separation. To tune FBG by resistant heat, some current is supplied into the wire. When the wavelength matched with one of the cavity modes of Sagnac loop filter, the mode-locked lasing is occurred. The electrical power sensitivity of the resonant wavelength is measured to 1.75pm/mW. This laser configuration can be applied the electrical power system for monitoring the power fluctuation.

• Korean Journal of Optics and Photonics
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• v.13 no.1
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• pp.15-20
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• 2002

We demonstrate a widely-tunable wavelength converter based on four-wave mixing in a semiconductor-fiber ring laser with no external pump light. Applying 10 GHz short pulses at -8 dBm as a probe signal, we achieve continuous wavelength tuning over the semiconductor optical amplifier gain-bandwidth reaching 30 nm down- and 17 m up-wavelength conversion. In addition to the wide tuning capability, the converter shows high-speed conversion and low saturation power capabilities.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.40 no.9
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• pp.666-672
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• 2003

In this paper, we described the fabrication and the performance of wavelength tunable distributed bragg reflector (DBR) laser diode (LD), having different waveguide coupling mechanisms; integrated-twin-guide (ITG) DBR-LD and butt coupled (BT) DBR-LD. This deviceis fabricated by metal organic vapor phase epitaxy (MOVPE) growth and planar buried heterostructure (PBH)-type transverse current confinement structure. The result of measurement, the optical performance of BT-DBR-LD is better over 2 times than that of ITG-DBR-LD at the variation of threshold current and output power, and slop efficiency due to the higher coupling efficiency of the butt coupled structure than the integrated twin guide structure. The maximum wavelength tuning range is about 7.2nm for ITG DBR-LD and 7.4nm for BT DBR-LD. Both types of lasers have a very high yield of single mode operation with a side-mode suppression ratio of more than 35dB.

• Korean Journal of Optics and Photonics
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• v.10 no.3
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• pp.248-253
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• 1999

In this paper, we have investigated a fiber type active coupler which utilizes the mode coupling between the side polished single mode optical fiber and the active multimode planar waveguide. The proposed device can be used for not only tunable wavelength filter or optical intensity modulator but also a tool for measuring optical properties of guiding material such as refractive index, birefringence, electro-optic coefficient, and thermo-optic coefficient. We gave designed and optimized a coupler structure using the BPM and fabricated the device using thermo-optic polymer as active planar waveguide overlay. The device showed that insertion loss was less then 0.5 dB, extinction ratio was -13 dB at the resonance wavelength, and the wavelength tunablity due to thermo-optic effect was -1.5 nm/$^{\circ}C$. The active coupler using thermo-optic effect can be used as a wavelength tunable filer, an optical intensity modulator and an optical sensor. pulses that are subsequently compressed by a dispersive optical fiber. Experimental results show that $sech^2$ shape pulses with a pulse width of ~14 ps and a time bandwidth product of ~0.34 are successfully generated at 10 GHz repetition rate. In contrast to other methods, such as higher order soliton compression, this approach does not depend on the optical power and thus shows promise for application to low-power lasers.