Chia-Yao Lo

Double-clad Cr 4+ :YAG crystal fiber amplifier

A novel double-clad Cr4+:YAG crystal fiber is demonstrated by use of a codrawing laser-heated pedestal growth method. Up to 10 dB of gross gain at a wavelength of 1.52 microm is achieved at a pump power of 0.83 W, which, to our knowledge, is the first Cr4+-doped fiber amplifier in the optical fiber communication band.

Glass-clad Cr4+:YAG crystal fiber for the generation of superwideband amplified spontaneous emission.

Glass-clad Cr4+:YAG crystal fiber is demonstrated by a codrawing laser-heated pedestal growth method. As much as 2.45 mW of superwideband amplified spontaneous emission (ASE) is generated in the optical fiber communication band with a 3-dB width of 240 nm. The simulation indicates that the ASE power could be in excess of 20 dBm for a 5-microm-diameter core at a pump power of 2.5 W.

Composition dependence of the microspectroscopy of Cr ions in double-clad Cr:YAG crystal fiber

We have demonstrated the use of microspectroscopy for measuring the Cr3+ and Cr4+ fluorescence spectra in double-clad Cr:YAG crystal fiber. The emission spectra of Cr3+ and Cr4+ are detected from core and inner cladding. The Cr3+ spectrum in the inner cladding shows a broad-band emission from 650to950nm, while the emission of Cr4+ occurs in the range of 1.15–1.55μm with a peak around 1.22μm. The characteristic of Cr ion at high-field sites shows a narrow-band emission (E2→A24 for Cr3+; E1→A23 for Cr4+), whereas that at low-field sites shows a broad-band emission (T24→A24 for Cr3+; T23→A23 for Cr4+). The emission intensity ratio of high-field sites to low-field sites in the inner cladding with different compositions has been investigated. It varies from 20% to 29% for Cr3+ and from 7.1% to 11.3% for Cr4+ when the concentration of SiO2 increases from 26.9to43.0wt%.

Intracavity and resonant Raman crystal fiber laser

We demonstrated an efficient, compact, and continuous-wave Raman crystal fiber laser (RCFL) using an intracavity and resonant χ(3) approach. The gain and nonlinear medium was Cr4+:Y3Al5O12 double-clad crystal fiber grown using the codrawing laser-heated pedestal growth technique. The RCFL threshold was only 50 mW, and the slope efficiency reached 14.3% above a pump power of 350 mW. The result is in good agreement with theory, which indicates a near-100% quantum efficiency of resonant stimulated Raman scattering.

High-Luminance White-Light Point Source Using Ce,Sm : YAG Double-Clad Crystal Fiber

Ce and Sm ions codoped yttrium aluminum garnet (Ce,Sm : YAG) double-clad crystal fibers (DCFs) were successfully fabricated using the codrawing laser-heated pedestal growth method. At a pump wavelength of 446 nm, white-light point source was produced from a 10--core DCF. The amplified spontaneous emissions and the residual pump resulted in a directional high brightness point source. A luminance of 4.5 × 109 cd/m2 was generated. The luminous flux of the point white light was 6.2 lm. When coupled to a 200-core multimode fiber, the output power and coupling efficiency were 4.8 mW and 36.8%, respectively. Point white-light sources are useful for biomedical endoscopic application and long-range directive illumination. The generated broadband yellow emission can also be served as the light source for optical coherence tomography system. Using the 91-nm yellow emission, an axial resolution of 1.5-optical coherence tomography can be achieved for ultrahigh-resolution ocular and industrial applications.

Characterization on broadband chromium-doped fiber amplifier

Up to 16-dB of gross gain at a wavelength of 1.47 /spl mu/m was achieved by a broadband Cr/sup 4+/:YAG fiber amplifier. The simulation indicates that the minimum noise figure is close to 3-dB at 1.24-1.6 /spl mu/m range.

The use of fluorescence confocal microscopy in mapping Cr/sup +3/ profile within the YAG crystal fiber

We have demonstrated the use of fluorescence confocal microscopy in mapping the Cr/sup +3/ profile within the YAG crystal fiber. A sensitivity of 2.3/spl times/10/sup 16//cm/sup 3/ was achieved, which is ten-fold of magnitude better than that of electron probe micro -analysis.

Fused-silica-clad Cr:YAG fiber

A low-propagation-loss (< 0.1 dB/cm) fused-silica-clad Cr:YAG fiber is demonstrated and investigated. The simulation shows that more than 0 dBm of amplified spontaneous emission could be generated with a 2-W pump and an 8-/spl mu/m core.

Highly-efficient Nd:YAG crystal fiber laser

Summary from only given. High quality gradient index crystal fibers were successfully grown by the laser heated pedestal growth (LHPG) technique. The distributed optical loss resulted mainly from the interface loss, which is estimated to be 0.3 cm/sup -1/. A laser output power of 80 mW was achieved with a slope efficiency of 28.9%.

Gradient-index Nd:YAG crystal fiber laser

Efficient Nd:YAG lasers were demonstrated using gradient-index crystal fibers. 75 mW of laser output power was achieved with a slope efficiency of 17.1%. Index difference of 0.0284 between the center and edge of the crystal fiber was observed.