Janet W. Lou

Experimental measurements of solitary pulse characteristics from an all-normal-dispersion Yb-doped fiber laser.

We demonstrate a solitary pulse output from an 8.3-MHz mode-locked Yb-doped fiber laser, operating entirely in the normal dispersion regime. The typical output hyperbolic-secant pulses have a 14-ps pulse width and a 1.2-mW average output power. The spectrum has steep band edges with a 6.1-nm width and a tunable center wavelength between 1050 and 1080 nm. Using a frequency-resolved optical gating setup, we show that the pulse intensity and phase profiles are consistent with a chirped soliton. Energy quantization is observed, thus demonstrating the non-parabolic nature of these pulses. The laser output is compressed to near the transform limit (approximately 430 fs).

4/spl times/10 GHz mode-locked multiple-wavelength fiber laser

We demonstrate a four-wavelength 10-GHz mode-locked erbium-doped fiber laser, with wavelength spacings of 3.5-5 nm. Nearly transform-limited Gaussian pulses of 11- to 14-ps duration are measured and all wavelengths are synchronous.

Frequency comb linewidth of an actively mode-locked fiber laser

We have measured the linewidth of frequency comb lines from a mode-locked fiber laser. The effective linewidth is 12 kHz over 5 ms, and the intrinsic linewidth is estimated to be less than 3 kHz

High-energy saturable absorber mode-locked fiber laser system

We demonstrate a mode-locked erbium-doped fiber laser with a 1-microm InGaAs saturable absorber that produces 84-ps, 1-nJ transform-limited pulses. Measurements of the InGaAs multiple quantum well revealed a slow saturable absorber that is useful for passive mode locking. Optical fiber was added to extend the cavity and vary the repetition rate from 51 kHz to 5.4 MHz. The narrow spectral width of the laser output (<0.04 nm) permits amplification to 0.2 microJ/pulse with minimal pulse broadening. Pulse energies as large as 1.7 microJ can be achieved with pulse widths of <330 ps. Average powers of 0.5 W at megahertz repetition rates are demonstrated.

Wideband frequency modulation of a mode-locked fiber laser

We have demonstrated wideband frequency modulation of the frequency comb lines of a high-repetition-rate fiber laser. With a modulation frequency of only approximately 10 kHz, we have generated modulation indices in excess of 250. Although internally modulated, the laser remains stable with 2-kHz linewidths, and thus the 10-kHz modulation sidebands are still clearly resolved even after propagation over several hundred kilometers. This unique characteristic is used for simultaneous measurement of propagation distances to 1-m resolution and velocities of less than 3 mm/s over a distance of greater than 50 km.

Remote atomic vapor magnetometer with Sub-pT resolution operating at ambient temperature

We have designed and characterized a Cesium vapor cell magnetometry system specifically aimed at meeting the challenges of remote interrogation. Standard single-mode telecom optical fibers are used for optical delivery and collection. The additional noise contribution due to optical polarization drift during propagation is mitigated by polarization and modal walk-off. We show that it is possible to obtain as low as 0.1 pT/Hz1/2 resolution at 1 Hz without temperature control over the ambient temperature range of -5 to 30 C.

Green and ultraviolet pulse generation with a compact, fiber laser, chirped-pulse amplification system for aerosol fluorescence measurements

We use a compact chirped-pulse amplified system to harmonically generate ultrashort pulses for aerosol fluorescence measurements. The seed laser is a compact, all-normal dispersion, mode-locked Yb-doped fiber laser with a 1050 nm center wavelength operating at 41 MHz. Average powers of more than 1.2 W at 525 nm and 350 mW at 262 nm are generated with <500 fs pulse durations. The pulses are time-stretched with high-dispersion fiber, amplified by a high-power, large-mode-area fiber amplifier, and recompressed using a chirped volume holographic Bragg grating. The resulting high-peak-power pulses allow for highly efficient harmonic generation. We also demonstrate for the first time to our knowledge, the use of a mode-locked ultraviolet source to excite individual biological particles and other calibration particles in an inlet air flow as they pass through an optical chamber. The repetition rate is ideal for biofluorescence measurements as it allows faster sampling rates as well as the higher peak powers as compared to previously demonstrated Q-switched systems while maintaining a pulse period that is longer than the typical fluorescence lifetimes. Thus, the fluorescence excitation can be considered to be quasicontinuous and requires no external synchronization and triggering.

Raman-pumped, dense dispersion-managed soliton transmission of 80 Gb/s OTDM data

The effects of radiation from dense dispersion-managed solitons into the normal-dispersion portion of their optical spectrum are observed for the first time in a novel Raman-pumped data transmission system. Filtering allows error-free propagation of 80-Gb/s OTDM data over 963 km.

Multiple-wavelength mode-locked erbium-doped fiber sigma laser

Summary form only given. We present a novel configuration for a two-wavelength erbium-doped fiber laser based on the sigma configuration. We show the setup of the multiple-wavelength sigma laser. The design allows single polarization operation using easily obtainable non-polarization maintaining components shown to the right of the polarization beam splitter. In this design, a 3-dB coupler is added after the erbium-doped fiber.

Characterization of atomic spin polarization lifetime of cesium vapor cells with neon buffer gas

The dephasing time of spin-polarized atoms in an atomic vapor cell plays an important role in determining the stability of vapor-cell clocks as well as the sensitivity of optically-pumped magnetometers. The presence of a buffer gas can extend the lifetime of these atoms. Many vapor cell systems operate at a fixed (often elevated) temperature. For ambient temperature operation with no temperature control, it is necessary to characterize the temperature dependence as well. We present a spin-polarization lifetime study of Cesium vapor cells with different buffer gas pressures, and find good agreement with expectations based on the combined effects of wall collisions, spin exchange, and spin destruction. For our (7.5 mm diameter) vapor cells, the lifetime can be increased by two orders of magnitude by introducing Ne buffer gas up to 100 Torr. Additionally, the dependence of the lifetime on temperature is measured (25 - 47 oC) and simulated for the first time to our knowledge with reasonable agreement.