Fiber Facet Research Articles

A surface mount single-mode laser module using passive alignment

A novel single-mode laser module has been developed using a surface mounting technique. A simple receptacle structure for the module output port is also designed. This module offers high coupling efficiency and optical coupling using the passive alignment technique. A module size of 7.6 mm/spl times/12 mm/spl times/3 mm is achieved, which is very friendly for the automatic assembly line as well as the module mounting process on circuit boards. A laser diode (LD) is passively positioned by utilizing a pair of alignment marks, each of which located on the LD and Si substrate, a single-mode fiber with a microhemispherical lens on the fiber facet is self-aligned on a Si-V groove. The LD to single-mode fiber coupling loss and standard deviation are found to be 5 dB and 1.5 db, respectively. The simple receptacle structure enables one to use this module in the same way as conventional surface mount electrical components. The module assembly process is simplified by successively mounting subassembly parts.

Photorefractive coupler for fault-tolerant coupling

We report the first experimental demonstration of a fault-tolerant laser-to-fiber coupler that is insensitive to both angular and lateral misalignments. Fault-tolerance is achieved by sending a laser beam into a photorefractive crystal that automatically senses and tracks the location of the fiber facet, and diffracts the input beam (via self-generated adaptive dynamic holograms) into the fiber. Using an argon laser (514.5 nm), a barium titanate crystal, and a multimode fiber (core diameter=400 μm, NA=0.16), we have achieved a coupling efficiency of 58% and a tolerance of more than 0.5 mm of lateral misalignment. Techniques to improve the coupling efficiency and the degree of fault tolerance, and to extend this method for the coupling of a laser diode output into a single-mode fiber are discussed.

Fiber-coupled self-mixing diode-laser Doppler velocimeter: technical aspects and flow velocity profile disturbances in water and blood flows

The effects of disturbances of the flow pattern in front of the fiber facet of a fiber-coupled self-mixing diode-laser Doppler velocimeter system are investigated. This was done by comparing measurements and calculations of the Doppler frequency spectrum with the expected values. The calculated Doppler spectrum was obtained from the calculation of light scattered (with or without Doppler shift) by the moving particles in front of the fiber facet. The velocity profile of the particles was calculated with a finite-element method. Measurements were done with water (with polystyrene spheres) and whole blood as the samples. Good agreement between measurements and calculations were obtained. The velocimeter was modeled as a five-mirror setup. The reflectivity of the fiber facet closest to the laser turns out to have the most influence on the sensitivity and stability of the laser. Direct reflection of unwanted light back into the laser cavity was avoided by placing a glass plate in front of the fiber. Design consi ations are presented.

Integrated coupling device between a laser diode and an optical fiber using a microlens

AbstractAn integrated coupling device between a GaAs/Al‐GaAs laser diode and an optical fiber using a microlens is described. It is calculated that the high single‐mode fiber coupling efficiency of 81 percent is obtained for the microlens with RMSA of 0.4 λ and that the large alignment tolerance of 55 μm is obtained in the z‐direction. It is demonstrated experimentally for single‐mode fiber coupling that the coupling efficiency is 26 percent and that the alignment tolerance in the z‐direction is 19 μm. the differences in the coupling efficiency and alignment tolerance between the calculation and experiment are due to a mismatch of beamwidth and the fabrication error of the fiber guide. Additionally, measurement of the oscillation spectrum of this coupling device, which has a composite cavity, showed that an LD with a microlens and fiber causes multimode oscillation due to reflection from the fiber facet.

Pr/sup 3+/-doped fluoride single-mode fiber laser

Laser oscillation at 1.312 mu m was achieved using a Pr/sup 3+/-doped fluoride single-mode fiber laser pumped at 1.017 mu m. The operation of a rare-earth-doped fiber laser at 1.31 mu m, which is one of the central wavelengths in conventional optical telecommunication trunk line systems, was demonstrated for the first time using Pr/sup 3+/ ion as an active ion. The laser cavity consists of a mirror and a cleaved fiber facet used as an output mirror. The maximum output power, threshold pump, and slope efficiency are 26 mW, 370 mW, and 9.86%, respectively.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Laser-diode-pumped mirror-free Er^3+-doped fiber laser

We have demonstrated 1.47-microm laser-diode-pumped Er(3+)-doped fiber laser operation at 1.552 microm, in which a cleaved fiber facet with 4% reflectivity is used as the output mirror. The pump source is a 1.47-microm InGaAsP laser diode inserted into the fiber laser cavity. End pumping a 7-m-long Er(3+)-doped fiber yields an output power of 1 mW for an absorbed pump power of 60 mW and a slope efficiency of 6.25%.

Effect of the Facet Radiator on the Coupling between a High Radiance LED and a Fiber

We investigated the problem of the coupling between a fiber and an edge emitting type LED having a similar structure as a DH laser by numerical calculation. To improve the efficiency εf of transmitting the light power generated in the diode to the light power coupled to the fiber, we introduced a radiator placed on the diode facet, and made a thorough study of the coupling, in which the fiber facet is close to the radiator head. The results obtained are as follows: (1) The efficiency εf is much higher when a semispherical radiator is employed than when the diode and the fiber are directly coupled. (2) A radiator having the shape of a truncated sphere or a sphere improves εf still more. (3) The binding agent between the diode and the radiator does not substantially decrease the effectiveness of radiators. (4) Radiators of optimum dimensions can be produced by polishing.