• Korean Journal of Optics and Photonics
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• v.13 no.4
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• pp.347-355
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• 2002

We have constructed a high efficiency and broad tunable cw Ti:sapphire laser with a four-mirror symmetric Z-type laser cavity to increase the laser usability. From theoretical analyses and experimental data for a symmetric Z-type laser cavity containing a Kerr medium, the cavity mode size and the Kerr-lens mode-locking (KLM) strength for KLM lasers can be confirmed as function of the position in the cavity, the intracavity laser power, and the stability parameter. As a result, the slope efficiency and the maximum average output power of cw Ti:sapphire laser at 5 W pumping power of Ar-ion laser were 31.3% and 1420 ㎽ respectively. The tunablility was ranged from 730 ㎚ to 908 ㎚ with average output power above 700 ㎽. We obtained the KLM operation easily by self-aperturing effect in the Kerr medium and the slope efficiency and the maximum average output power of KLM Ti:sapphire laser was 16% and 550 ㎽ respectively. The spectral bandwidth was 33 ㎚ at the center wavelength of 807 ㎚ and the pulse width was 27 fs with a repetition rate of 82 ㎒.

• Proceedings of the Materials Research Society of Korea Conference
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• 2012.05a
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• pp.87.2-87.2
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• 2012

고출력 반도체 레이저 다이오드는 발진 파장 및 광 출력에 따라 다양한 분야에 응용되고 있으며, 특히 발진파장이 808 nm 및 1470 nm 인 고출력 레이저 다이오드의 경우 재료가공, 펌핑용 광원 (DPSSL, 광섬유 레이저), 의료, 피부미용 (점 제거), 레이저 다이오드 디스플레이 등 가장 다양한 응용분야를 가진 광원 중의 하나라고 할 수 있다. 일례로 재료가공의 경우, 레이저 용접, 레이저 인쇄, 하드디스크의 레이저 텍스쳐링 등 그 응용분야는 무수히 많으며, 최근에는 미래 성장동력 사업의 하나로 중요한 이슈가 되는 태양전지에서 에지 분리 (edge isolation), ID 마킹, 레이저 솔더링 등에서 필수불가결한 광원으로 각광받고 있다. 808 nm 대역 In(Ga)AlAs quantum dots laser diode (QDLD) 성장을 위하여 In(Ga)AlAs QD active 와 In(Ga)AlAs QD LD 성장으로 크게 분류하여 여러 가지 test 실험을 수행하였다. 우선 In(Ga)AlAs QD LD 성장에 앞서 high power LD에 적용 가능한 GaAs/AlGaAs quantum well의 성장 및 전기 측정을 수행하여 그 가능성을 보았다. In(Ga)AlAs QD active layer의 효과적인 실험 조건 조절을 위해 QD layer는 sequential mithod (ex. n x (InGaAlAs t sec + InAs t sec + As 10 sec)를 사용하였다. In(Ga)AlAs QD active layer는 성장 온도, 각 sequence 별 시간, 각 source 양, barrier 두께 조절 및 타입변형, Arsenic flux 등의 조건을 조절하여 실험하였다. 또한 위에서 선택된 몇 가지 active layer 를 이용하여 In(Ga)AlAs QD LD 성장 조건 변화를 시도하였다.

• Proceedings of the Optical Society of Korea Conference
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• 2002.07a
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• pp.226-227
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• 2002

처프펄스증폭(CPA) 개념을 이용한 티타늄 사파이어 레이저는 고출력 펨토초 펄스 생성에서 표준적인 시스템이며, 현재 수 kHz의 반복률에서 TW 급의 출력을 가지는 시스템들이 개발되어 사용 중이다.(1) 그러나 증폭시에 나타나는 티타늄 사파이어 레이저 매질에서의 이득 좁아짐 효과 때문에 얻어지는 최소 펄스폭은 20 펨토초 수준으로 제한된다. 이러한 스펙트럼폭의 한계를 극복하기 위하여 hollow-fiber에서의 자체위상변조(SPM) 현상을 이용하여 500 nm 이상의 파장 영역에 걸친 continuum을 발생시키는 기술이 제안되었다. (중략)

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.38 no.3
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• pp.174-184
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• 2001

Wavelength tunable fiber ring laser can be tuned by causing a resonance on the optical path having the least loss which is controlled by a polarization adjustment. It is observed that lasing wavelengths having 1 nm FSR(Free Spectral Range) can be tuned over the range of 1540~1560 nm when a polarization controller and an intra-cavity polarizer are adjusted. The tuning mechanism can be expected by analyzing the characteristics of the laser output using an optical path model and the concept of a birefringence loss. It is found that the constructive interference between longitudinal modes of different optical paths may cause wavelength tuning in the fiber ring laser.

• Korean Journal of Optics and Photonics
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• v.12 no.1
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• pp.5-9
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• 2001

A wavemeter was realized using the phenomena that the phase lag between principal polarization states in an optical retarder is a function of wavelength. The change in the polarization state of the optical beam as it passes through the optical retarder is dependent on wavelength. The wavelength of the optical beam is determined by comparing the power difference between principal polarization states. A prototype wavemeter was successfully implemented using a polarization maintaining fiber with birefringence $3\times10^{-4}$ and length 100 mm as the optical retarder. The measurement resolution was 0.08 nm over a wavelength region of 1554.38 nm-1557.l9 nm, which agreed well with theoretically calculated results. In addition, the dependence of operating characteristics on temperature was analyzed theoretically and experimentally.mentally.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.18 no.8
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• pp.2037-2042
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• 2014

Three methods for gain saturation tone application were compared for optical wavelength division multiplexing transmission using more than 32 channels. The methods are to use high power distributed feedback laser diodes, to use amplified light sources, and lastly to use one saturation tone and several WDM light sources. 1532.3 nm, 1545.7 nm, and 1558.2 nm for the wavelength dependency of the saturation tone were also compared. As a result, the effect of amplified spontaneous emission noise caused by an amplifier was very slight. long wavelength for a saturation tone caused 1 dB gain reduction and its reason was analyzed.

• Korean Journal of Optics and Photonics
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• v.15 no.5
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• pp.455-460
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• 2004

We have developed a mode-locked ultra-short pulse C $r^{4+}$:YAG laser, as well as a continuous wave C $r^{4+}$:YAG laser. The laser was pumped by a Nd:YAG laser and its characteristics were investigated. In continuous wave mode, we obtained as much as 600 mW at 1.436 ${\mu}{\textrm}{m}$ with pumping power of 6 W, by using an output coupler with a reflectivity of 98%. The power slope efficiency was 10%, when the gain medium was cooled to 19$^{\circ}C$. The tuning range was varied from 1.39 ${\mu}{\textrm}{m}$ to 1.55 ${\mu}{\textrm}{m}$ and the maximum power was 400 mW at 1.492 ${\mu}{\textrm}{m}$ with a 3-plate birefringent filter. The C $r^{4+}$:YAG laser was mode-locked by a Kerr lens mode locking method. Mode locking at 1.436 ${\mu}{\textrm}{m}$was initiated by slightly rocking a mirror mount. But the pulses were very unstable because of the strong water absorption at this region. So we shifted the lasing wavelength to 1.492 ${\mu}{\textrm}{m}$ by using a 3-plate birefringent filter. Then we obtained stable state mode-locking with the maximum average power of 280 mW for a pumping power of 6 W. The pulse width of 43 fs was measured using an autocorrelator and the repetition rate was 104.5 MHz.

• Korean Journal of Optics and Photonics
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• v.15 no.1
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• pp.17-21
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• 2004

We demonstrate an S/S＋band discretely tunable thulium doped fiber laser (TTDFL), anchored on a 50-㎓ ITU-T grid. Investigating the inversion analysis of the thulium doped fiber (TDF) in applying a dual wavelength (1.4 m and 1.5 m) pumping scheme, a laser whose tuning range covers most of the S/S＋band has been obtained. Within the wide 3-㏈ bandwidth of 65.1 nm, the output power of the tunable laser exceeds 6.1 ㏈m with very flat spectral profile and the number of DWDM channels generated is as large as 178. If we increase the subsidiary pump power to 22 ㎽, the bandwidth is expanded up to 66.2 nm. By controlling the temperature of the fine grid filter, we have also shown that the frequency locking capability of the laser can be improved. The laser developed in this work is expected to be utilized as a practical optical source providing reference wavelengths in the S/S＋band.

• Journal of The Institute of Information and Telecommunication Facilities Engineering
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• v.3 no.2
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• pp.51-60
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• 2004

In this paper, 8-channel multiplexer with 100GHz channel spacing is fabricated. The 8-channel multiplexer is fabricated by connecting three cascaded Mach Zehnder Interferometer (MZI) of optical fiber type, and each interferometer has the wavelength interval of 100GHz, 200GHz and 400GHz, respectively. furthermore, to acquire uniform insertion loss, it is fabricated by using Wavelength Flatten Coupler (WFC) in which the variation of insertion loss is low. Especially, the variation of wavelength interval in the output is explicitly simulated as a function of optical path difference, and the wavelength coupling process along with cascaded connection is discussed. $CO_2$ laser to adjust precisely the wavelength. In summary, The prototype composed by eight cascaded MZI has an insertion loss of 2.1dB, the bandwidth of 0.8nm at 5.5dB point, and channel crosstalk of 25dB Furthermore, the loss dependent on polarization is measured as 0.06dB.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.38 no.2
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• pp.1-5
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• 2001

We propose an optical performance monitoring method for WDM optical transmission systems. By assigning a pair of AWG ports to each optical signal channel. the optical power, optical signal-to-noise ratio (OSNIO, and wavelength of all the signal channels are observed simultaneously. The output power ratio of the AWG port pair depended on the wavelength variation of the channel with sensitivity of 1dB/0.026nm. The OSNH results were deviated no more than 0.7dB from the results measured by optical signal analyzer (OSA).