Do Il Chang

Efficient cascaded Raman generation and signal amplification at 1.3 μm in GeO2-doped single-mode fibre

We demonstrate a high-gain, cascaded fibre Raman amplifier, operating at 1.3 pm. Raman generation and amplification are achieved in a ring resonator constructed solely from fused fibre WDM couplers with low-loss GeOz-doped single mode fibre used as the active medium. The amplifier is pumped by a Nd:YAG laser at 1.064 p.m. In our resonant cascaded geometry, this generates the third Stokes line at 1.24 pm, which acts as a pump for Raman amplification of signals around 1.3 km. A gain of 28 dB is demonstrated with output signal powers of up to 20 dBm for 3.4 W of pump power. Our experiments also indicate the important role of filters to suppress feedback in the resonator, permitting high Raman gain and good signal quality. 0 1997 Elsevier Science B.V.

A novel intra-cavity for efficient cascaded Raman generation using WDM couplers

A novel intra-cavity with a broadband spectral response is designed and demonstrated to deliver a 4th order Stokes cascaded Raman generation. A large transmission bandwidth of 295 nm is realized using the two WDM couplers. The results applied to a Raman fiber laser operating at 1706 nm wavelength using a 1313 nm pump source are reported.

Dual-wavelength cascaded Raman fiber laser

We have investigated the characteristics of a dual-wavelength cascaded Raman laser based on a composite resonator configuration using a fiber WDM coupler and two pairs of fiber Bragg gratings. The WDM coupler, which served to form a ring cavity and acted as an output coupler simultaneously, made the laser system simple and effective. Since the WDM coupler is made by the fused biconical taper technique and has the characteristic of periodic transmission windows, it can be designed to resonate at wavelengths corresponding to high odd Stokes orders simultaneously.

Raman shifting of Nd:YAP laser radiation with a Brillouin resonator coupled with a Raman half-resonator

We demonstrate the efficient generation of first Stokes Raman radiation using a Brillouin resonator coupled with a Raman half-resonator. A Raman laser at the eye-safe wavelength of 1.575 mum in high-pressure CH(4) gas was generated from a passively Q-switched Nd:YAP laser. Raman conversion efficiencies of as much as 55% were obtained at a pressure of 800 psi.

Short pulse generation in the mode-locked fibre laser using cholesteric liquid crystal

Abstract We have demonstrated short pulse generation from an optical fibre laser system utilizing a cholesteric liquid crystal (CLC) as a circular polarizing mirror to induce passive mode-locking mechanism. Along with a piezoelectric-transducer phase modulator, mode-locking laser pulses of 1.8 ps with 2.8 nm spectral bandwidth at repetition rate of fundamental and several harmonic frequencies have been obtained in a simple Fabry–Perot cavity configuration.

Efficient first stokes generation using a Brillouin resonator coupled with a Raman half resonator

We report an efficient Raman laser system which utilizes stimulated Brillouin scattering as a dual-cavity resonator mirror for fundamental and Raman waves. A Raman laser at the eye-safe wavelength of 1.54 µ m is generated in high pressure CH4 gas from a passively Q-switched Nd:YAG laser. Employing a meniscus lens with an optimized reflectance of 10% at the fundamental wavelength, a maximum Raman energy of 33 mJ with a residual fundamental energy of 20 mJ has been obtained, where the pressure of CH4 gas is 800 psi.

All-optical wavelength conversion for 20-Gb/s RZ format data

We have successfully demonstrated an all-optical wavelength conversion scheme for high-speed return-to-zero (RZ) format data input by using a semiconductor-optical-amplifier (SOA) converter incorporated with a stabilized asymmetric Mach-Zehnder interferometer (AMZI). A bit-error-rate penalty of the converted signals less than 1.2 dB compared to that of the back-to-back signals was achieved for the entire wavelength conversion range from 1530 to 1560 nm with an AMZI. In this scheme, the conversion speed faster than the carrier recombination rate of the SOAs was possible. Noninverted wavelength conversion of 20-Gb/s RZ format data signals has been achieved.

Mode-locked Fabry-Perot fiber laser using cholesteric liquid crystal mirror

Summary form only given. Recently, mode-locked erbium fiber lasers have been intensively studied as candidates for inexpensive and compact short pulse sources. In this paper we propose a novel mode-locked fiber laser utilizing the selective reflection properties of a cholesteric liquid crystal (CLC) which acts as a circularly polarizing mirror to induce mode-locking mechanism along with the nonlinear polarization evolution (NPE) and suppresses the spatial hole burning arising in a Fabry-Perot cavity.

All-optical demultiplexing scheme based on an optical parametric loop mirror

Summary form only given. In recent years, several application schemes based on four wave mixing (FWM) effect in optical parametric loop mirror (PALM), such as wavelength interchange, wavelength conversion and spectral inversion, have been proposed. The generated FWM wave appears to be relatively strong compared to the input signal and control beams used in those scheme, and can be easily separated out from the other beams. In this paper, we demonstrate, the first time to our knowledge, an all-optical demultiplexing of 10 GHz optical input pulses into 2.5 GHz pulses using the PALM.

Effects of polarization evolutions inside the cholesteric liquid crystal cell on the output characteristics of ring type fiber lasers

Among the liquid crystal devices, the cholesteric liquid crystals (CLC) are known to have interesting optical properties because of their peculiar molecular structures, through which the overall displacement of an optical beam traces out a helical path. When an unpolarized light is incident at the CLC cells, one of the circular polarizations whose electric vectors are rotating along the helical path of layers is almost transmitted and the other one rotating in the opposite direction is almost reflected if the wavelength of incident light is in multiples of the rotation pitch. We report experimentally observed and theoretically analyzed output characteristics of fiber lasers with the CLC cell inserted as a polarization device into the fiber cavity.