• Journal of the Korean Institute of Electrical and Electronic Material Engineers
• /
• v.18 no.7
• /
• pp.628-634
• /
• 2005

We have simulated and proposed novel optical cavity, which has two elliptical mirrors, for NDIR gas sensor module and have tested it from 0 ppm to 2,000 ppm $CO_2$ concentration. The proposed sensor module shows the maximum peak voltage at 500 ms pulse modulation time, however, it shows a maximum voltage changes at 200 ms pulse duration with 18,000 times amplification gain. From 0 ppm to 2,000 ppm, the voltage difference of sensor module $({\Delta}V)$ shows 360 mV at 200 ms pulse duration and 3 sec turn-off time. The response time of designed sensor module is about 30 seconds.

• Proceedings of the Optical Society of Korea Conference
• /
• 2000.02a
• /
• pp.126-127
• /
• 2000

Resonance fluorescence is the manifestation of the interaction between the physical system under consideration and the vacuum-field fluctuation. The fluorescence spectrum provides such physical informations as the energy-level structure of the system, instabilities and relative populations of the energy levels, etc.. One of the typical fluorescence spectra is the Mollow triplet appearing when two-level atoms are driven by a strong coherent field in free space$^{(1)}$ . In the weak field limit, the singlet instead of the triplet is obtained with a reduced linewidth due to the squeezing of one quadrature phase of the induced atomic dipole$^{(2)}$ . On the other hand, when the atoms are put inside a cavity rather than in free space, a doublet spectrum due to the vacuum Rabi-splitting is achieved, showing clearly the coupling of atoms and the cavity in the single-quantum limit$^{(3)}$ . (omitted)

• Journal of the Optical Society of Korea
• /
• v.19 no.2
• /
• pp.130-135
• /
• 2015

Based on the extended nonlinear Schr$\ddot{o}$dinger equation, the influences of the filter effect on pulse splitting in a passively mode-locked erbium-doped fiber laser with positive dispersion cavity are investigated theoretically. Numerical results show that, as the bandwidth of the spectral filter decreases, the nonlinear chirp appended to the pulse increases under the combined action of the filter effect of the super-Gaussian spectral filter and the self-phase modulation effect. On further decreasing the bandwidth, the wave breaking of the pulse takes place. In addition, by varying the pump power of the laser or the profile of the spectral filter, the influences of the filter effect on pulse splitting also change accordingly.

• Current Optics and Photonics
• /
• v.1 no.5
• /
• pp.544-550
• /
• 2017

This simulation based study reports a novel tunable, compact, room temperature terahertz (THz) transistor source, operated on the concept of charge plasma oscillation with the capability of radiating within a terahertz gap. A vertical cavity with a quasi-periodic distributed-Bragg-reflector has been attached to a THz plasma wave transistor to achieve a monochromatic coherent surface emission for single as well as multi-color operation. The resonance frequency has been tuned from 0.5 to 1.5 THz with the variable quality factor of the optical cavity from 5 to 290 and slope efficiency maximized to 11. The proposed surface emitting terahertz transistor is able to satisfy the demand for compact solid state terahertz sources in the field of teratronics. The proposed device can be integrated with Si CMOS technology and has opened the way towards the development of silicon photonics.

• Proceedings of the Optical Society of Korea Conference
• /
• 1989.02a
• /
• pp.13-19
• /
• 1989

Passive mode-locking of a pulsed Nd:YAG laser is achieved with saturable absorbers, BDN dye in iodoethane solvent and Kodak Eastman # 26 dye in 1,2-dichloroethane solvent, and its optimum conditions are investigated. The thickness of saturable absorbers employed in the laser mode-locking is 0.16~0.50mm. The PBR (peak-to-background ratio) measured in the oscilloscope is 79.8% in Kodak Eastman # 26 dye at the neighbourhood of the peak power, whereas the passive mode-locking with BDN dye gives PBR of 67.7%. BDN and Kodak Eastman # 26 dyes are superior in photostability over Kodak eastman # 9860 and # 9740 dyes which were used previously in passive mode-locking. From the PBR curve, we find that Kodak Eastman # 26dye is more effective than BDN dye in passive mode-locking. The spacing between the adjacent pulses of the pulse train, which depends on the laser cavity length, is measured and is found to be 7 nsec for the cavity length of 100cm.

• The Bulletin of The Korean Astronomical Society
• /
• v.46 no.2
• /
• pp.61.1-61.1
• /
• 2021

Squeezed light는 중력파 검출기의 양자 잡음을 줄여 측정의 민감도를 향상시키기 위해 사용하는 양자 광원이다. Squeezed light는 광학적 손실에 민감하기 때문에 중력파를 측정하기 위해서는 정밀한 mode matching이 필요하다. 하지만 mode mismatching은 실제 실험 상황에서 동적으로, 그리고 무작위로 나타나므로 정밀하게 조정하기 어렵다. Mode mismatching에 견고한 squeezed light를 만들기 위해서는 multimode squeezed light가 필요하다. Multimode squeezed light를 만드는 방법으로 는 self-imaging cavity를 이용하여 생성하는 방법이 대표적으로 알려져 있다. 이 발표에서는 self-imaging cavity 기반으로 만든 optical parametric oscillator(OPO) 에서 생성된 squeezed light가 기존 OPO로 생성한 squeezed light 보다 여러 spatial mode mismatching (위치, 방향, 크기 빗맞음)에 대해 견고함을 소개한다.

• Journal of the Optical Society of Korea
• /
• v.13 no.3
• /
• pp.316-320
• /
• 2009

A novel broadband wavelength-swept Raman laser was used to implement Fourier-domain mode locked (FDML) swept-source optical coherence tomography (SS-OCT). Instead of a conventional semiconductor optical amplifier, this study used broadband optical fiber Raman amplification, over 50 nm centered around 1545 nm, using a multi-wavelength optical pumping scheme, which was implemented with the four laser diodes at the center wavelengths of 1425, 1435, 1455 and 1465 nm, respectively, and the maximum operating power of 150 mW each. The operating swept frequency of the laser was determined to 16.7 kHz from the FDML condition of 12 km optical fiber in the ring cavity. The OCT images were obtained using the novel broadband wavelengthswept Raman laser source.

• Current Optics and Photonics
• /
• v.5 no.2
• /
• pp.186-190
• /
• 2021

In this study, a compact, picosecond, mid-infrared 3.8 ㎛ MgO:PPLN optical parametric oscillator (OPO) laser output with high peak power is realized using a master oscillator power amplifier (MOPA) 1 ㎛ solid-state laser seeded by a picosecond fiber laser as the pump source. The pump source was a 50 MHz and 10 ps fiber seed source. After AOM pulse selection and two-stage solid-state amplification, a 1,064 nm laser output with a repetition frequency of 1-2 MHz, pulse width of 9.5 ps, and a maximum average power of 20 W was achieved. Furthermore, a compact short cavity with a unsynchronized pump is adopted through the design of an OPO cavity structure. When the injection pump power was 15 W and the repetition frequency was 1 MHz, the average output power of idler light was 1.19 W, and the corresponding peak power was 119 kW. The optical conversion efficiency was 7.93%. When the repetition frequency was increased to 2 MHz, the average output power of idler light was 1.63 W, the corresponding peak power was 81.5 kW, and the optical conversion efficiency was 10.87%. At the same time, the output wavelength was measured at 3,806 nm, and the beam quality was MX2 = 3.21 and MY2 = 3.34.

• Proceedings of the Korean Vacuum Society Conference
• /
• 2015.08a
• /
• pp.78-78
• /
• 2015

Metamaterials, artificially structured nanomaterials, have enabled unprecedented phenomena such as invisibility cloaking and negative refraction. Especially, hyperbolic metamaterials also known as indefinite metamaterials have unique dispersion relation where the principal components of its permittivity tensors are not all with the same signs and magnitudes. Such extraordinary dispersion relation results in hyperbolic dispersion relations which lead to a number of interesting phenomena, such as super-resolution effect which transfers evanescent waves to propagating waves at its interface with normal materials and, the propagation of electromagnetic waves with very large wavevectors comparing they are evanescent waves and thus decay quickly in natural materials. In this abstract, I will focus discussing our efforts in achieving the unique optical property overcoming diffraction limit to achieve several extraordinary metamaterials and metadevices demonstration. First, I will present super-resolution imaging device called "hyperlens", which is the first experimental demonstration of near- to far-field imaging at visible light with resolution beyond the diffraction limit in two lateral dimensions. Second, I will show another unique application of metamaterials for miniaturizing optical cavity, a key component to make lasers, into the nanoscale for the first time. It shows the cavity array which successfully captured light in 20nm dimension and show very high figure of merit experimentally. Last, I will discuss the future direction of the hyperbolic metamaterial and outlook for the practical applications. I believe our efforts in sub-wavelength metamaterials having such extraordinary optical properties will lead to further advanced nanophotonics and nanooptics research.

• Journal of Korean society of Dental Hygiene
• /
• v.4 no.2
• /
• pp.153-163
• /
• 2004

There are normal inhabitants doing medically useful functions in the body. There are many kinds of bacteria performing specific functions in the oral cavity. Two strains of lactic acid bacteria were isolated from normal inhabitants of children 's oral cavity, which inhibited the the production of halitosis by anaerobic bacteria. The authors identified the isolates by the lest using API 50 CHL medium kit. 1. Two isolates were Gram-positive bacilli and produced hydrogen peroxide. 2. The optical density was 1.286 in the supernatant of Fusobacterium nucleatum after vortexing for 30 minutes, whereas in the supernatant of combined Fusobacterium nucleatum and each isolate, they were reduced to 0.628 and 0.497, which the percentages of coaggregation between them were 29.4% and 57.8%, respectively. 3. The optical density of Fusobacterium nucleatum precipitate was 1.794 in the culture media containing cysteine and $FeSO_4$, being reduced to 1.144 and 0.915 in the coaggregated precipitates of Fusobacterium nucleatum and each isolate. 4. The optical density of Porphyromonas gingivalis precipitate was 1.932 in the culture media, being reduced to 1.170 and 1.266 in the coaggregated precipitates of Porphyromonas gingivalis and each isolate. 5. When two isolates were tested with API 50 CHL medium kit, those were identified as Lactobaciallius salivarius and Lactobacillus delbrueckii subsp. lactis.