• Laser Solutions
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• v.17 no.3
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• pp.19-23
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• 2014

To directly engrave circuit-line patterns as wide as $6{\mu}m$ in a buildup film to be used as an IC substrate, we applied a projection ablation technique in which an 8 inch dielectric ($ZrO_2/SiO_2$) mask, a DPSS 355nm laser instead of an excimer laser, a ${\pi}$-shaper and a galvo scanner are used. With the ${\pi}$-shaper and a square aperture, the Gaussian beam from the laser is shaped into a square flap-top beam. The galvo scanner before the $f-{\theta}$ lens moves the flat-top beam ($115{\mu}m{\times}105{\mu}m$) across the 8 inch dielectric mask whose patterned area is $120mm{\times}120mm$. Based on the results of the previous research by the authors, the projection ratio was set at 3:1. Experiments showed that the average width and depth of the engraved patterns are $5.41{\mu}m$ and $7.30{\mu}m$, respectively.

• Journal of the Korean Institute of Telematics and Electronics D
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• v.35D no.6
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• pp.92-98
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• 1998

The transform limited optical short pulses are generated by compression of pulses from a gain switched distributed feedback laser at 5 GHz repetition rate. The gain-switched pulses have the minimum pulse width of 27 psec with the spectral width of 1.1 nm. Thus the output pulses have a large amount of linear chirp and nonlinear chirp. We suppress the nonlinear chirp by passing the pulses through the optical band pass filter with 3 dB band width of 0.55 nm which is narrower than spectral width of the input pulses and generate 7.1 psec pulses by compressing the output with the dispersion compensating fiber. The pulses have time-bandwidth product of 0.49 which is close to the transform limited gaussian pulse. These pulses can be utilized as optical sources in 40 Gbit/s time division multiplexed optical transmission system.

• Korean Journal of Optics and Photonics
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• v.14 no.1
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• pp.92-96
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• 2003

Dielectric apertures in vertical cavity laser have been used for improved device performance. Numerical analysis is used to estimate the optical losses as the aperture diameter is reduced. The optical losses depend on the aperture size, thickness and location. The optical loss strongly depend on the aperture size and thickness when the aperture size is similar or smaller than the emitted wavelength. The optical loss is negligible and not depend on the aperture thickness when the aperture size is larger than 5 times emitted wavelength.

• Korean Journal of Optics and Photonics
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• v.12 no.4
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• pp.257-262
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• 2001

A Littman type tunable external-cavity diode laser system was developed. The laser output which is the Oth-order diffracted beam from a diffraction grating in an external cavity is a single longitudinal mode. Its FWHM was measured as less than 9 MHz. With the diode driving current of 140 mA and operating temperature of $25^{\circ}C$, the coarse tuning range of 3.475 urn was measured. A fine tuning experiment in which an external mirror was rotated by a PZT driven by a sawtooth wave was performed, and its tuning range of 0.042 urn was measured. sured.

• Journal of IKEEE
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• v.15 no.4
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• pp.313-318
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• 2011

The effects of external continuous wave optical injection on spectral comb of a 10 GHz harmonically mode-locked semiconductor fiber ring laser have been studied. Greater than 40 dB spectral deeps in the spectral comb and greater than 30 dB reduction of supermode beating noise are achieved by injecting coherent light with ~ 100 KHz spectral width. To examine the possibility of using a low-cost seed source, we replace the seed source by a DFB laser with ~ 10 MHz spectral width. It shows similar spectral deeps, however supermode beating noise enhancement, rather than reduction, is observed.

• Journal of Sensor Science and Technology
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• v.28 no.1
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• pp.23-29
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• 2019

A copper tetracumylphenoxy phthalocyanine (CuPccp) thin film was formed on an organic insulator film by Langmuir-Blodgett (LB) deposition for gas sensor fabrication. To increase the reproducibility of film transfer, stearyl alcohol was used as a transfer promoter. The structural properties of the CuPccp layers were optically monitored through attenuated total reflection and polarization-modulated ellipsometry techniques. The average thickness of a single layer of the CuPccp LB film was measured to be 2.5 nm. Despite the role of the transfer promoter, the stability of the layer transfer was not sufficient to ensure homogeneity of the LB film. This was probably due to the presence of aggregates in the molecular structure of the CuPccp LB film. Nevertheless, copper phthalocyanine polymorphism can be greatly suppressed by the LB arrangement, which appears to contribute to the improvement of electrical conductivity. The p-type semiconductor characteristics were confirmed by Hall measurements from the CuPccp LB films.

• Korean Journal of Optics and Photonics
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• v.21 no.6
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• pp.254-258
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• 2010

We investigate an optical technique for beam shaping and optical amplification of a pulsed laser diode without variation of its original properties, such as repetition rate and pulse duration. The horizontal and longitudinal sizes of the pulsed laser diode are 300 and $2{\mu}m$, respectively, and its output power is $1.1mW/cm^2$. The multimodal and elliptical pulse shape of the laser diode is converted to the single-modal and Gaussian pulse shape by using a lensed optical fiber. Since the single-modal lensed fiber coupling from the multimodal pulsed laser diode degrades the output power severely, the output power of the pulsed laser diode is dramatically enhanced by using an optical amplification method based on master oscillated power amplification (MOPA). The pulse qualities of the laser diode are not changed after amplifying the pulse power and the output power was finally measured to be $29mW/cm^2$.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.45 no.8
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• pp.17-23
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• 2008

We have investigated the properties of the novel rectangular ring lasers containing active and passive regions in a InP material system. The rectangular ring laser consists of four low loss total internal reflection mirrors and a directional coupler made out of passive three waveguide. Two different lasers haying active lengths of 250 and $350{\mu}m$ and total cavity lengths of 580 and $780{\mu}m$ are fabricated, respectively. For both devices lasing thresholds of 38 mA is obtained at room temperature and under continuous wave operation. Lasing is predominantly single mode with the side mode suppression ratio better than 20 dB.

• Korean Journal of Optics and Photonics
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• v.18 no.4
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• pp.270-273
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• 2007

We have investigated the output characteristics of the 946 nm Nd:YAG laser which is longitudinally pumped by a fiber coupled laser diode. The temperature of a Nd:YAG crystal mount was kept constant by a controller with thermoelectric cooler. As a result, we measured more intense output at a low temperature, and then the maximum output power was measured to be 870 mW when the pumping power and the temperature were 9.95 W and $5^{\circ}C$, respectively. It appeared that output was decreased above 10 W pump power because of the thermal effects in gain medium.

• Korean Journal of Optics and Photonics
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• v.22 no.4
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• pp.179-183
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• 2011

An external cavity laser operating at near infrared wavelength is demonstrated by incorporating polymer waveguide Bragg reflectors. 3rd order Bragg grating and oversized rip waveguide structure were designed by using the effective index method and the transmission matrix method. The polymer waveguide was fabricated using polymer materials with refractive indices of 1.462 and 1.435 for the core and the cladding layers, respectively. The external feedback laser with 875-nm Bragg grating exhibits single mode lasing located at 850-nm wavelength with an output power of 0 dBm, a 20-dB bandwidth of 0.2 nm and a side mode suppression ratio of 40 dB.