Fiber ring laser

Fig. 6.37 Basic principle of fiber ring laser with positive and negative dispersion parts of the fiber. The pump laser is coupled into the fiber ring by a wavelength-division multiplexed coupler (WDM)...

L.E. Nelson, D.J. Jones, K. Tamura, H.A. Haus, E.P. Ippen, Ultrashort-pulse fiber ring lasers. Appl. Phys. B 65, 277 (1997)... 

I.N. Duling III, All-fiber ring soliton laser mode locked with a nonlinear mirror. Opt. Lett. 16(8), 539 (1991) ... 

An interesting realization of a widely tunable OPO is a fiber OPO pumped by a fiber laser. One example is the sub-1 pm operation of a fiber OPO in a fiber ring resonator, pumped by an all-fiber master oscillator plus power amplifier based on a photonic crystal fiber as gain medium [592], A conversion efficiency of 8 6 % from the pump at 1079nm to the anti-Stokes signal at 715nm. This means a frequency shift of 142 THz between pump and anti-Stokes signal. 

The fiber optic refractive index sensor finds use in biomedical applications. It uses a silicon chip with optical waveguides forming ring resonators. When the laser wavelength is scanned, the resonators cause dips in the power transmitted through the device. The wavelength at which these dips occur is a measure of the refractive index of the substance in contact with the chip surface. 

The system consists of a water cooled ring adapter with purge air supply (Figure 29) and of a control and evaluation unit. The laser beam with an excitation wavelength of 1064 nm is focused in the measurement volume by a light fiber and the enhanced thermal radiation is captured by an appropriate detector head perpendicularly. It can be applied directly in the raw exhaust without dilution up to exhaust gas peak temperatures of 700°C. Its sensitivity (3 (ig/m3) and variability for realtime (20 Hz) soot characterizing in different applications is shown. 

The first equation is realized at the LKB while the second one is carried out at the LPTF. A first titanium-sapphire laser excites the hydrogen transition. A laser diode (power of 50 mW) is injected by the LD/Rb standard and frequency doubled in a LiBsOs (LBO) crystal placed in a ring cavity. The generated UV beam is frequency compared to the frequency sum (made also in a LBO crystal) of the 750 and 809 nm radiations produced by a second titanium-sapphire laser and a laser diode. A part of the 809 nm source is sent via one fiber to the LPTF. There, a 809 nm local laser diode is phase locked to the one at LKB. A frequency sum of this 809 nm laser diode and of an intermediate CO2 laser in an AgGaS2 crystal produces a wave at 750 nm. This wave is used to phase lock, with a frequency shift S, a laser diode at 750 nm which is sent back to the LKB by the second optical fiber. This 750 nm laser diode is frequency shifted by lyfCOo) + S with respect to the one at 809 nm. In such a way, the two equations are simultaneously satisfied and all the frequency countings are performed in the LKB. Finally, the residual difference between the two titanium-sapphire lasers is measured with a fast photodiode or a Schottky diode. 

Figure 24.14 The left panel is a plan of the testing area near the LENS (reflected shock) tunnel 1 — 8 test section 2 — TDL probe 3 — 4 nozzle M = 8-16 4 — 8" reflected shock tube 5 — fiber optic and signal line conduit 6 — data acquisition and 7 — TDL system optical table. The right panel is a schematic diagram of the setup used to record water-vapor absorption in high-enthalpy flows 1 — InGaAs detectors 2 — tunable diode laser Ai = 1400.74 nm 3 — ring interferometer 4 — tunable diode laser A2 = 1395.69 nm and 5 — HoO reference cell...

The illumination is provided by a laser diode in the near infrared at 830 nm. To avoid any specific orientation of the polarization of the light, the 4.8 mm-wide beam is directed by an optical fiber to a colhmator and then to an optical device made of a Glan-Foucault prism and qnarter-wave plate. An equatorial ring (inner diameter 118 mm) with vacnnm tight optical windows is inserted in the wall of the low-pressnre chamber in which the agglomeration of the dnst particles takes place. A set of analyzers allows measnrements to be obtained at 22 phase angles on a series of different phase angles, almost uniformly distribnted from 10 to 165 [63]. 

Fig. 5.11. (a) Spin-coated polymer 1 films (40-80 nm thick, with refractive index (n 1.70) are coated on a transparent 200-nm-thick film of chemical vapor deposited parylene (n 1-67), forming a two-layer index-matched waveguide on glass (n 1.45). (b) Spin-coated polymer 1 films (40nm) coated on DFB gratings fabricated from PDMS. (c) Ring-mode laser structure produced by dip-coating polymer 1 on a 25 mm diameter silica optical fiber... 

---