Christoffer Renner

Recovery of spectral features readout with frequency-chirped laser fields

A data-processing technique is proposed for use with conventional frequency-chirped absorption spectroscopy to ensure accurate mapping of spectral features into time-domain signatures with arbitrarily fast readout chirp rates. This technique recovers the spectrum from a signal that is distorted owing to the fast chirp rate and therefore facilitates fast measurement of the spectral features over a broad spectral range with high resolution. Both numerical simulations and experimental results are presented.

Compressive laser ranging.

Compressive sampling has been previously proposed as a technique for sampling radar returns and determining sparse range profiles with a reduced number of measurements compared to conventional techniques. By employing modulation on both transmission and reception, compressive sensing in ranging is extended to the direct measurement of range profiles without intermediate measurement of the return waveform. This compressive ranging approach enables the use of pseudorandom binary transmit waveforms and return modulation, along with low-bandwidth optical detectors to yield high-resolution ranging information. A proof-of-concept experiment is presented. With currently available compact, off-the-shelf electronics and photonics, such as high data rate binary pattern generators and high-bandwidth digital optical modulators, compressive laser ranging can readily achieve subcentimeter resolution in a compact, lightweight package.

Broadband photonic arbitrary waveform generation based on spatial-spectral holographic materials

We discuss an approach for the practical implementation of photonic arbitrary waveform generation of microwave signals. We describe and demonstrate an approach using spatial-spectral (S2) holography in rare earth ion doped crystals that has the potential to achieve extremely wide bandwidths (>40 GHz) using conventional electro-optic phase modulators and low bandwidth (<100 MHz) control electronics. We provide analysis of this approach, show simulations, and perform experimental demonstrations of the technique. We show a pulse compression factor of ~15,000 and demonstrate the largest effective bandwidth of 3.8 GHz to date for pulse compression using S2 holography. We also show control and manipulation of up to 30 independent compressed pulses for the creation of arbitrary waveforms.

Linearization of ultra-broadband optical chirps for precision length metrology

We demonstrate precise active linearization of ultra-broadband (>5 THz) laser frequency sweeps using a self-heterodyne technique. Frequency errors less than 170 kHz relative to linearity were observed enabling very high resolution ranging over large distances.

Conditions for highly efficient anti-Stokes conversion in gas-filled hollow core waveguides.

Using a four-mode theoretical analysis we show that highly efficient anti-Stokes conversion in waveguides is more challenging to realize in practice than previously thought. By including the dynamics of conversion to 2(nd) Stokes via stimulated Raman scattering and four-wave mixing, models predict only narrow, unstable regions of highly efficient anti-Stokes conversion. Experimental results of single-pass Raman conversion in confined capillary waveguides validate these predictions. This places more stringent conditions on systems that require highly efficient single-pass anti-Stokes conversion.

Photonic chirp compression and arbitrary waveform generation for micro and millimeter-wave applications

A novel approach for the practical implementation of photonic arbitrary waveform generation of microwave signals is explored. Here we describe and demonstrate linear sideband chirp compression over 4 GHz bandwidth with a compression factor of < 15000.

Recovery technique for chirped readout of spectral features

A data processing technique is proposed for use with conventional absorption spectroscopy at arbitrarily fast frequency chirp rates to map spectral features accurately into time-domain signatures. Numerical simulations and experimental results are presented.