• Proceedings of the Korean Society of Precision Engineering Conference
• /
• 2001.04a
• /
• pp.964-967
• /
• 2001

Aspherical lens with the higher numerical aperture has been needed in the optical storage device to increase the recording density on the disk. However, high numerical aperture means the large slope angle at the clear aperture of the lens. Therefore, the measurement and manufacturing technique including the lens molding process for the slope angle should be developed. In this paper, the evaluation technique was described for the optical performance of the aspherical lens. Aspherical form error brings about the wavefront error and the side lobe of the beam intensity profile. A schematic diagram of the aspherical lens manufacturing was drawn to explain the aspherical form error compensation. Finally, form error of the aspherical lens was defined and plotted using the raw data of the Formtalysurf.

• Current Optics and Photonics
• /
• v.1 no.3
• /
• pp.214-220
• /
• 2017

A wavelength filter based on a polymer Bragg reflector has received much attention due to its simple structure and wide tuning range. Tilted Bragg gratings and asymmetric Y-branches are integrated to extract the reflected optical signals in different directions. To optimize device performance, design procedures are thoroughly considered and various design parameters are applied to fabricated devices. An asymmetric Y-branch with an angle of $0.3^{\circ}$ produced crosstalk less than -25 dB, and the even-odd mode coupling was optimized for a grating tilt angle of $2.5^{\circ}$, which closely followed the design results. Through this experiment, it was confirmed that this device has a large manufacturing tolerance, which is important for mass production of this optical device.

• Journal of the Optical Society of Korea
• /
• v.16 no.2
• /
• pp.127-132
• /
• 2012

This study discusses photoresist forming using a composite grayscale to fabricate a Fresnel lens. Grayscale lithography is a common production method used to facilitate the forming of lenses with different curvatures and depths. However, this approach is time consuming and expensive. This study proposes a method for overcoming these obstacles by integrating a digital micromirror device and microscope to supplant the traditional physical grayscale mask. This approach provides a simple and practical maskless optical lithography system. According to the results, the two adjacent grayscales displayed substantial differences between the high grayscale and influence the low grayscale that ultimately affected photoresist formation. Furthermore, we show that change of up to 150% in the slope can be achieved by changing the grayscale gradient in the central zone and the ring profile. The results of the optical experiment show a focus change with different gray gradients.

• Korean Journal of Optics and Photonics
• /
• v.26 no.6
• /
• pp.318-321
• /
• 2015

We demonstrate a frequency-resolved optical grating (FROG) device for measuring the intensity and phase versus time of several-tens-of-picoseconds laser pulses, using a thick nonlinear optical crystal. The huge pulse-front tilt generated by a holographic grating increases the temporal range of the device, which can make a single-shot measurement of laser pulses less than 100 ps in duration. To verify the measurement technique, we generate double pulses using a Michelson interferometer. The measured duration of a single pulse is about 300 fs and the measured maximum delay of two pulses is 60 ps, which implies that the proposed FROG device can measure laser pulses with maximum pulse width of about 120 ps.

• Electrical & Electronic Materials
• /
• v.9 no.1
• /
• pp.44-50
• /
• 1996

In this study, Selenium device was fabricated by vacuum evaporation method with the substrate temperature at room temperature and its electrical and optical properties were investigated to be used in optical device. The film properties largely depended on the transmittance and annealing time, and improved with aging owing to stress release. We found that the photocurrent of the films increase linearly with light illumination. As a result, Selenium device made by this method yielded a short circuit current density of 10.5mA/$\textrm{cm}^2$, an open circuit voltage of 39OmV.

• Journal of the Optical Society of Korea
• /
• v.17 no.4
• /
• pp.296-299
• /
• 2013

A low density lipoprotein (LDL) cholesterol testing device, structured with serial reflected face-to-face mirror (SRM) allowing spectrophotometry measurements, is presented. The spectrophotometry has been employed to measure the amount of light that a sample absorbs, but it generally should have had path length longer than 10 mm to secure enough sensitivity. Such requirement of path length has often been problematic in implementing a thin type of lab on a disc (LOD). We developed the SRM system which was implemented in a detection chamber with 1.4mm thickness, providing path length longer than 10mm, and thus straightforwardly being applicable to LOD as thin as a compact disc. The experimental results show that the SRM system gives not only a much thinner design compared to the conventional spectrophotometry-based LOD but also a comparable performance to already commercialized spectrometers.

• Proceedings of the IEEK Conference
• /
• 2001.06e
• /
• pp.9-12
• /
• 2001

Optical aligning process to archive the maximum optical coupling is crucial in many optical device manufacturing line such as laser diode module. Due to the three-dimensional nature of housing module and the aligning process for laser diode coupler, large amount of the manufacturing time, typically ranging from tens of minutes to an hour has to be devoted to the aligning process alone. In this thesis, we propose a new optical aligning process that employee a two-pass algorithm: coarse-to-fine search. Coarse search is a kind of blind search that finds the candidate region where the maximum optical coupling might mostly occur, followed by a fine searching that finds the maximum within the candidate region. The algorithm has been tested on 50 samples of cam-type laser diode modules, and the experimental results are analyzed in terms of aligning time and coupling efficiency.

• Korean Journal of Optics and Photonics
• /
• v.33 no.5
• /
• pp.210-217
• /
• 2022

In this paper, a study is conducted on the acceptable tolerance of an alignment device to reduce the optical loss caused by the alignment tolerance of a window hermetic optical connector. To increase the transmission distance of optical signals and fiber-optic communication systems, it is necessary to maintain and improve the high optical efficiency of the connectors used to bond optical fibers. In the case of the window hermetic optical connector, the optical system is aligned through an alignment device. At this time, since the two connectors are used together, each component is fixed, and further alignment is impossible. The alignment tolerance of the housing system and pin used to align the optical system of the connector causes optical loss, leading to serious problems in the fiber-optic communication system. Thus, to find the acceptable tolerance required for manufacturing the optical-connector alignment device, tolerance analysis is performed on the components of the optical connector, such as the ball lens and the window. We also implement single-mode and multimode optical-connector systems, respectively. Based on the results, we determine an acceptable tolerance value for the alignment device.

• JSTS:Journal of Semiconductor Technology and Science
• /
• v.4 no.1
• /
• pp.63-73
• /
• 2004

A simple analytical model has been presented for the study of the optical bistability using a $GaAs-Al_{0.32}Ga_{0.68}As$ multiple quantum well (MQW) p-i-n diode structure. The calculation of the optical absorption is based on a semi-emperical model which is accurately valid for a range of wells between 5 and 20 nm and the electric field F< 200kV/cm . The electric field dependent analytical expression for the responsivity is presented. An attempt has been made to derive the analytical relationship between the incident optical power ( $(P_{in})$ ) and the voltage V across the device when the diode is reverse biased by a power supply in series with a load resistor. The relationship between $P_{in}$ and $P_{out}$ (i.e. transmitted optical power) is also presented. Numerical results are presented for a typical case of well size $L_Z=10.5nm,\;barrier\;size\;L_B=9.5nm$ optical wave length l = 851.7nm and electric field F? 100kV/cm. It has been shown that for the values of $P_{in}$ within certain range, the device changes its state in such a way that corresponding to every value of $P_{in}$ , two stable states and one unstable state of V as well as of $P_{out}$ are obtained which shows the optically controlled bistable nature of the device.

• Journal of the Korean Society for Precision Engineering
• /
• v.18 no.4
• /
• pp.25-36
• /
• 2001