Abstract: A fiber-laser-based implementation of a Gigahertz source through difference frequency generation (DFG) by nonlinear optical (NLO) materials is compact, tunable and scalable. A pair of pulsed fiber lasers, preferably single-frequency, generate output pulses at frequencies ?1 and ?2 that overlap temporally. A beam combiner combines the laser outputs and routes the combined output to a GHz generator head where a nonlinear interaction process in the NLO material generates GHz radiation.

Abstract: A phosphate glass 1-?m fiber ASE source provides high power and broadband emission that covers wavelengths on the short side of Yb-doped silica. A single-mode fiber formed from phosphate glass is doped with highly elevated concentrations of Yb dopants 0.5-30 wt. % and typically 2-10 wt. %, far higher than either silica or germano-silicate. The high concentration of Yb dopant absorbs the pump in a short length, typically 10-150 cm instead of tens of meters, to provide high saturated output power and a shifted emission spectrum. The excess power allows the fiber ASE source to be configured to provide the output powers, emission bandwidth and stability desired by many applications. Furthermore, the ASE can be configured to emit a nearly Gaussian spectral profile without sacrificing power or bandwidth.

Abstract: A phosphate glass 1-?m fiber ASE source provides high power and broadband emission that covers wavelengths on the short side of Yb-doped silica. A single-mode fiber formed from phosphate glass is doped with highly elevated concentrations of Yb dopants 0.5-30 wt. % and typically 2-10 wt. %, far higher than either silica or germano-silicate. The high concentration of Yb dopant absorbs the pump in a short length, typically 10-150 cm instead of tens of meters, to provide high saturated output power and a shifted emission spectrum. The excess power allows the fiber ASE source to be configured to provide the output powers, emission bandwidth and stability desired by many applications. Furthermore, the ASE can be configured to emit a nearly Gaussian spectral profile without sacrificing power or bandwidth.

Abstract: A 2-?m fiber Amplified Spontaneous Emission (ASE) source provides a wide emission bandwidth and improved spectral stability/purity for a given output power. The fiber ASE source is formed from a heavy metal oxide multicomponent glass selected from germanate, tellurite and bismuth oxides and doped with high concentrations, 0.5-15 wt. %, thulium oxides (Tm2O3) or 0.1-5 wt% holmium oxides (Ho2O3) or mixtures thereof. The high concentration of thulium dopants provide highly efficient pump absorption and high quantum efficiency. Co-doping of Tm and Ho can broaden the ASE spectrum.

Abstract: A heavy metal oxide glass selected from germanate, tellurite and bismuth oxide glasses provides a host for highly efficient Thulium doped 2 ?m oxide glass and fiber lasers. The concentration of Thulium ions is high enough that energy transferred by the phenomenon of cross-relaxation will enhance laser emission at 2 ?m and suppress emission at 1.5 ?m so that 2 ?m emission is dominant.

Abstract: A low-noise, high-gain optical image amplifier includes a multi-mode pump source that injects optical energy into an active fiber's inner cladding to excite the dopant ions in a 2-D array of doped cores and provide gain. The cores are arranged to sample and collect light from an image incident on one end of the fiber, amplify the light and output an amplified pixilated image at the other end of the fiber. The multi-core active fiber preserves the spatial pattern and spectrum of the incident image. The cores may be configured as single-mode cores to preserve phase information or multi-mode cores to scramble the phase information. It is often desirable for the gain to be approximately uniform across the 2-D array. This can be achieved by pumping uniformly doped cores into their respective saturation regions.

Abstract: A distributed fiber sensor based on spontaneous Brillouin scattering uses a single-frequency fiber laser as a source and a cw Brillouin fiber ring laser as an OLO to optically shift the frequency of the OLO to set the Brillouin/OLO beat frequency within the bandwidth of a conventional heterodyne receiver. The distributed fiber sensor is capable of real-time measurement of both temperature and strain.

Abstract: A single-frequency Brillouin fiber ring laser with extremely narrow linewidth comprises a single-frequency narrow-linewidth rapid-tunable pump laser, a temperature-controlled acoustically-damped package for Brillouin fiber ring laser cavity, and an auto-tracking feedback electronic loop with novel configuration for active stabilization. The Pound-Drever-Hall frequency-locking technique is employed to keep pump laser frequency in resonance with one of the Brillouin fiber ring cavity modes. Instead of changing cavity length of Brillouin fiber ring laser, the pump laser frequency is rapidly tuned in the auto-tracking feedback electronic loop. This enables extremely narrow linewidth radiation emitted from a Brillouin fiber ring laser without stretching the fiber ring.

Abstract: A compact, inexpensive and rugged fiber collimating lens and lens array achieve large beam diameters and provide long working distances. A special single-mode fiber is inserted between a standard single-mode input fiber and a GRIN fiber lens, typically quarter-pitch or slightly longer. The specialty fiber condenses the mode field diameter (MFD) of the beam in the input fiber into its smaller MFD. As a result, the fiber collimating lens provides greater beam expansion due to the larger divergence angle of the specialty fiber, which in turn provides longer working distances.

Abstract: A compact single frequency, single-mode 2 ?m fiber laser with narrow linewidth, <100 kHz and preferably <100 kHz, is formed with a low phonon energy glass doped with triply ionized rare-earth thulium and/or holmium oxide and fiber gratings formed in sections of passive silica fiber and fused thereto. Formation of the gratings in passive silica fiber both facilitates splicing to other optical components and reduces noise thus improving linewidth. An increased doping concentration of 0.5 to 15 wt. % for thulium, holmium or mixtures thereof produces adequate gain, hence output power levels for fiber lengths less than 5 cm and preferably less than 3 cm to enable single-frequency operation.

Abstract: A fiber-laser-based implementation of a Terahertz source through difference frequency generation (DFG) by nonlinear optical (NLO) crystals is compact, tunable and scalable. A pair of fiber lasers (Q-switched, CW or mode-locked) generate single-frequency outputs at frequencies ?1 and ?2. A fiber beam combiner combines the laser outputs and routes the combined output to a THz generator head where a nonlinear interaction process in the NLO crystal generates THz radiation.

Abstract: A compact single frequency, single-mode 1 ?m fiber laser with narrow linewidth (<10 kHz) and high output power (>2 mW) is formed with an oxide-based multi-component glass fiber doped with triply ionized rare-earth ytterbium ions and fiber gratings formed in sections of passive silica fiber and fused thereto. The multi-component glass supports higher doping concentrations than standard silica fiber, hence higher output power levels in short cavities. Formation of the gratings in passive silica fiber both facilitates splicing to other optical components and reduces noise thus improving linewidth.

Abstract: A short laser cavity (up to 30 cm in length) comprising a free-space tunable MEMS Fabry-Perot filter, a collimating lens and a section of erbium-doped phosphate gain fiber (2-25 cm) is formed between a pair of broadband reflectors. The cavity is optically pumped to excite the erbium ions and provide gain, which establishes an initial longitudinal mode structure that spans the C-band with a mode spacing of at least 0.3 GHz and a roundtrip unsaturated gain of at least 8 dB over the tuning range. A controller tunes the MEMS filter, which has a filter function whose spectral width is at most ten and preferably less than four times the longitudinal mode spacing, to align its transmission maxima to one of a plurality of discrete output wavelengths that span the C-band. A thermal control element adjusts the longitudinal mode structure to align a single mode with the transmission maxima of the filter.

Abstract: A compact, inexpensive and rugged fiber collimating lens and lens array achieve large beam diameters and provide long working distances. A special single-mode fiber is inserted between a standard single-mode input fiber and a GRIN fiber lens, typically quarter-pitch or slightly longer. The specialty fiber condenses the mode field diameter (MFD) of the beam in the input fiber into its smaller MFD. As a result, the fiber collimating lens provides greater beam expansion due to the larger divergence angle of the specialty fiber, which in turn provides longer working distances.

Abstract: Thermally dissimilar glass fibers are fusion spliced by pretreating the cleaved end surface of the high-temperature fiber to provide a smooth surface for making good contact with the low-temperature fiber. The fibers are heated to a temperature that is high enough to soften the low-temperature fiber but not the high-temperature fiber and brought in contact to form the fusion joint.

Abstract: A tellurite-based glass composition for use in EDFAs exhibits higher phonon energy without sacrificing optical, thermal or chemical durability properties. The introduction of boron oxide (B2O3) into the Er3+-doped tellurite glasses increases the phonon energy from typically 785 cm?1 up to 1335 cm?1. The inclusion of additional glass components such as Al2O3 has been shown to enhance the thermal stability and particularly the chemical durability of the boro-tellurite glasses. Er:Yb codoping of the glass does further enhance its gain characteristics.

Abstract: Phosphate glass fibers are an attractive alternative to silica fibers because they can be co-doped with much higher concentrations of Yb and Er and exhibit a higher optical gain per unit length. However, in such fibers the absorption of the pump is high and heating effects caused by the pump laser can cause a significant change in refractive index. This problem is overcome with a phosphate glass composition that exhibits a temperature coefficient of refractive index &bgr;=dn/dT close to zero. This is achieved by avoiding alkali metal oxides in the glass composition and by adjusting the concentration of the network modifiers such as BaO.

Abstract: A compact low-cost continuous single-mode fiber laser delivers output powers in excess of 50 mW over the C-band (1530 nm-1565 nm). The phosphate glass fiber supports the high doping concentrations of erbium and ytterbium (Er:Yb) without self-pulsation that are required to provide sufficient gain per centimeter needed to achieve high power in the ultra short cavity lengths necessary to support single-mode lasers. The use of fiber drawing technology provides a lower cost solution than either combined solution doping/MCVD fiber fabrication or waveguide fabrication. The ability to multi-mode clad pump the fiber further reduces cost, which is critical to the successful deployment of fiber lasers in the burgeoning metro markets.

Abstract: A short laser cavity (up to 30 cm in length) comprising a free-space tunable MEMS Fabry-Perot filter, a collimating lens and a section of erbium-doped phosphate gain fiber (2-25 cm) is formed between a pair of broadband reflectors. The cavity is optically pumped to excite the erbium ions and provide gain, which establishes an initial longitudinal mode structure that spans the C-band with a mode spacing of at least 0.3 GHz and a roundtrip unsaturated gain of at least 8 dB over the tuning range. A controller tunes the MEMS filter, which has a filter function whose spectral width is at most ten and preferably less than four times the longitudinal mode spacing, to align its transmission maxima to one of a plurality of discrete output wavelengths that span the C-band. A thermal control element adjusts the longitudinal mode structure to align a single mode with the transmission maxima of the filter.

Abstract: A multi-port optical amplifier chip has an inner cladding layer sandwiched between a pair of outer cladding layers, a plurality of active core elements disposed substantially within the inner cladding layer to receive optical signals at respective input ports and transmit amplified optical signals at respective output ports, a pair of reflecting surfaces on opposing sides of the inner cladding and at least one pump source. The pump source directs pump light into the inner cladding layer where it is confined to bounce back-and-forth across the active core elements thereby enhancing the absorption of pump light into the core elements, hence increasing gain. Greater than 5 dB over the C-band (1930 nm-1965 nm) in less than 10 cm is expected with a phosphate glass material co-doped with greater than 2 weight percent Erbium and 10 weight percent Ytterbium. A number of fiber drawing based approaches are contemplated for manufacturing the amplifiers to achieve this performance and reduce cost.