Wideband-tuneable, nanotube mode-locked, fibre laser

Ultrashort-pulse lasers with spectral tuning capability have widespread applications in fields such as spectroscopy, biomedical research and telecommunications1–3. Mode-locked fibre lasers are convenient and powerful sources of ultrashort pulses4, and the inclusion of a broadband saturable absorber as a passive optical switch inside the laser cavity may offer tuneability over a range of wavelengths5. Semiconductor saturable absorber mirrors are widely used in fibre lasers4–6, but their operating range is typically limited to a few tens of nanometres7,8, and their fabrication can be challenging in the 1.3–1.5 mm wavelength region used for optical communications9,10. Single-walled carbon nanotubes are excellent saturable absorbers because of their subpicosecond recovery time, low saturation intensity, polarization insensitivity, and mechanical and environmental robustness11–16. Here, we engineer a nanotube–polycarbonate film with a wide bandwidth (>300 nm) around 1.55 mm, and then use it to demonstrate a 2.4 ps Er31-doped fibre laser that is tuneable from 1,518 to 1,558 nm. In principle, different diameters and chiralities of nanotubes could be combined to enable compact, mode-locked fibre lasers that are tuneable over a much broader range of wavelengths than other systems

ELECTRONICALLY TUNABLE, 1.55-MUM ERBIUM-DOPED FIBER LASER

The authors thank W. Miniscalco of GTE for supplying the fiber used. P. F. Wysocki acknowledges the fellowship support of the National Science Foundation. This research was supported by Litton Systems, Inc

WAVELENGTH STABILITY OF A HIGH-OUTPUT, BROAD-BAND, ER-DOPED SUPERFLUORESCENT FIBER SOURCE PUMPED NEAR 980-NM

We report the dependence of the mean wavelength of Er-doped superfluorescent fiber sources on temperature, pump wavelength, and pump power. In particular, we measure an intrinsic temperature coefficient of between -2 and +8 parts in 10(6) (ppm) per degree Celsius depending on pump wavelength, pump power, and fiber length. Additionally, we report a pump wavelength dependence that is symmetrical about the peak pump absorption wavelength (near 976 nm) and a decrease in mean wavelength with pump power with a slope of between 0 and -93 ppm/mW.This research was supported by Litton Systems, Inc. The research of P. F. Wysocki is partially supported by the National Science Foundation. The authors are grateful to AT&T for providing the Er-doped fiber used in this study

BROAD-SPECTRUM, WAVELENGTH-SWEPT, ERBIUM-DOPED FIBER LASER AT 1.55-MU-M

This research was supported by Litton Systems Inc

STABLE FIBER-SOURCE GYROSCOPES

This research was supported by Litton Systems, Inc

CHARACTERISTICS OF ERBIUM-DOPED SUPERFLUORESCENT FIBER SOURCES FOR INTERFEROMETRIC SENSOR APPLICATIONS

The fcharacteristics of 1.55 mum Er-doped superfluorescent fiber sources (SFS's), intended for fiber-optic gyroscope (FOG) applications, are explored theoretically and experimentally. With proper selection of the source configuration, fiber length, pump wavelength, pump power, and fiber composition, we show that it is possible to meet the stringent requirements of the FOG, including a high output power, broad emission bandwidth, and excellent spectral thermal stability. Variations of the mean wavelength, spectral width, and output power of the SFS with fiber length, pump power, pump wavelength, and temperature are modeled for representative sources pumped near 980 nm or 1.48 mum, and are shown to be in good agreement with experimental results. The effects of a multimoded pump, erbium ion pair, and optical feedback are also assessed. This study indicates that the Er-doped SFS is an excellent candidate for the FOG and for other applications requiring spatial coherence and low temporal coherence.The authors thank AT&T for supplying the Er-doped fiber

Silicon-nanocrystal-coated silica microsphere thermooptical switch

We report on a low-switching-energy, all-optical fiber switch that consists of a silica microsphere resonator coated with a silica layer containing silicon nanocrystals. A signal at 1450 mn and a pump at 488 nm are coupled into the microsphere through a tapered fiber. When a pump pulse is launched into the sphere, it is absorbed by the nanocrystal layer, causing the sphere to heat up and change its refractive index. The index change can be exploited to switch the signal by shifting the microsphere resonance. A resonance wavelength shift of 5 pm, sufficient to fully switch the signal, was observed with a pump pulse energy of only 85 W. The rise time of the switch was similar to 25 ms (limited by the pump peak power) and its fall time was similar to 30 ms (limited by the sphere's thermal time constant). The product of the switching peak power (3.4 mu W) and the device's characteristic dimension (a diameter of 150 mu m) is 5.1 x 10(-10) Wm, one of the lowest values reported for an all-optical fiber switch