Jason M. Auxier

PbS quantum-dot-doped glasses for ultrashort-pulse generation

We investigate the use of PbS quantum-dot-doped glasses as saturable absorbers for ultrashort-pulse lasers by means of absorption bleaching experiments and numerical analysis of the pulse shaping process using the Haus’ master equation. We explain the mode-locking mechanism and the limitations of these absorbers. The generation of transform-limited fs pulses is predicted by soliton mode locking initiated by the absorption saturation of higher excited states of the quantum-dot saturable absorber.

Room-temperature gain at 1.3 μm in PbS-doped glasses

We report on room-temperature optical gain at the ground exciton transition of PbS quantum-dot-doped glasses while optical pumping into the next-higher exciton resonance. The material gain in the quantum dots is as large as 80 cm−1. The dot-size selective excitation provides tunability of the optical gain. This is demonstrated by tuning the gain from 1317 to 1352 nm by changing the pump wavelength from 900 to 980 nm.

Ion-exchanged waveguides in glass doped with PbS quantum dots

The lowest-loss (≲1dB∕cm) ion-exchanged waveguides in glass doped with PbS quantum dots are presented. Near-field mode profile and refractive index profile using the refracted near-field technique were measured for these waveguides. We demonstrate that the optical properties of this glass remain unchanged during the ion-exchange process.

Silver and potassium ion-exchanged waveguides in glasses doped with PbS semiconductor quantum dots

We present a detailed analysis of potassium-sodium and silver-sodium ion-exchange processes for fabricating waveguides in glass doped with PbS semiconductor quantum dots. We compare the propagation losses of these waveguides, and we discuss the sources of these losses. In addition, we demonstrate a fourfold reduction in the propagation loss previously reported for potassium-sodium ion-exchanged waveguides and show that waveguides can be produced at additional quantum-dot resonances using both methods. We show that the near-infrared optical properties of these quantum dots remain intact by comparing the waveguide and bulk (unguided) luminescence spectra. Measurements of the near-field mode profiles show a high level of field confinement, which make these waveguides ideal for nonlinear optical (high-intensity) applications.

Quantum dots for fiber laser sources

In this invited paper, we will discuss the use of quantum dots as nonlinear optical elements in fiber laser sources. Furthemore, a review of the fabrication of the first low-loss (< 0.5 dB/cm) ion-exchanged waveguides in a quantum-dot-doped glass will be presented. We will discuss the coupling, propagation, absorption, and scattering losses in these waveguides. The near-field mode profile along with the refractive index profile of these waveguides will be presented. This PbS quantum-dot-doped glass was chosen due to its attractive optical gain and bleaching characteristics at wavelengths throughout the near infrared. This bleaching of the ground-state optical transition has been utilized for passive modelocking of a variety of lasers in the near infrared. In addition, we will discuss some of the potential integrated and fiber optics applications of our quantum-dot-doped waveguides.

Small mode-size waveguides in quantum-dot-doped glasses by Ag-film ion exchange

We present a silver-sodium ion-exchange process for fabricating small mode-size waveguides in glass doped with PbS semiconductor quantum dots. We show that the process does not alter the optical properties of the quantum dots by comparing the waveguide and bulk luminescence spectra. We also show that the optical mode is highly confined. This field confinement produces high optical intensities, which are essential for nonlinear optical applications.

Recovery dynamics of a PbS quantum dot doped glass passive mode locker

Summary form only given. Recently we demonstrated that PbS quantum dot doped glasses, fabricated by thermal treatment of an oxide molten glass, can be used as intracavity saturable absorbers to obtain self-starting mode locking in infrared solid-state lasers. In particular, using these absorbers in a Cr:forsterite laser we obtained pulses as short as 4.6 ps with a time-bandwidth product of 0.35 and pulse energies up to 1 nJ. Because of the large exciton Bohr radius (18 nm) and the small band gap energy (0.4 meV at RT) these saturable absorbers are suitable for operation over a wide spectral rang from visible to 3 /spl mu/m. However, it was unclear why shorter pulses then 4.6 ps could not be obtained. Here we perform degenerate pump-probe experiments to address this point and determine the recovery time of the optical nonlinearity.

Active micro and nano-structured glass fiber and waveguide devices

Optical and electron confinement are utilized to tailor the optical characteristics of active materials and photonic devices. A technique to incorporate semiconductor quantum dots into planar glass waveguides with low propagation loss is demonstrated. The waveguides are fabricated by potassium-sodium and silver-sodium ion exchange processes in glasses that contain PbS quantum dots with radii of a few nanometers. The unique optical properties of the quantum dots are preserved throughout the waveguide fabrication process. We also demonstrate novel compact fiber lasers based on active, highly doped fibers with photonic crystal cladding. The flexibility provided by microstructuring the fiber enables improved fiber laser performance and several Watts of laser output are generated from few centimeters of active fiber.