Carl Farrell

Octave-spanning super-continuum from a silica photonic crystal fiber pumped by a 386 MHz Yb:fiber laser

We report octave-spanning super-continuum generation in a silica photonic crystal fiber (PCF) pumped by a compact, efficient, mode-locked all-normal dispersion Yb:fiber laser. The laser achieved 45% optical-to-optical efficiency by using an optimized resonator design, producing chirped 750 fs pulses with a repetition rate of 386 MHz and an average power of 605 mW. The chirped pulses were compressed to 110 fs with a loss of only 4% by using multiple reflections on a pair of Gires-Tournois interferometer mirrors, yielding an average power of up to 580 mW. The corresponding peak power was 13.7 kW and produced a super-continuum spectrum spanning from 696-1392 nm.

87Rb-stabilized 375-MHz Yb:fiber femtosecond frequency comb

We report a fully stabilized 1030-nm Yb-fiber frequency comb operating at a pulse repetition frequency of 375 MHz. The comb spacing was referenced to a Rb-stabilized microwave synthesizer and the comb offset was stabilized by generating a super-continuum containing a coherent component at 780.2 nm which was heterodyned with a (87)Rb-stabilized external cavity diode laser to produce a radio-frequency beat used to actuate the carrier-envelope offset frequency of the Yb-fiber laser. The two-sample frequency deviation of the locked comb was 235 kHz for an averaging time of 50 seconds, and the comb remained locked for over 60 minutes with a root mean squared deviation of 236 kHz.

Two-photon laser-assisted device alteration in silicon integrated-circuits

By inducing two-photon absorption to perturb the switching characteristics of sensitive transistors located within the active layer of a proprietary 28-nm silicon test chip, we demonstrate time-resolved nonlinear laser-assisted device alteration.

Aberration analysis based on pinhole-z-scan method near the focal point of refractive systems

In this work we present a method used to study the spherical and chromatic aberrations contribution near the focal point of a refractive optical system. The actual focal position is measured by scanning a pinhole attached on the front of a power detector, which are scanned along the optical axis using a motorized stage with 1 μm resolution. Spherical aberration contribution was analyzed by changing the pupil aperture, by modifying the size of the input iris diaphragm and for each case, measuring the actual laser power vs the detector position. Chromatic aberration was analyzed by performing the same procedure but in this case we used an ultra-broad-band femtosecond laser. The results between ML and CW operation were compare. Experimental results are presented.

Solid-immersion-lens-enhanced nonlinear frequency-variation mapping of a silicon integrated-circuit

By inducing two-photon absorption within the active layer of a proprietary silicon test chip, we demonstrate solid-immersion-lens-enhanced nonlinear frequency-variation mapping of a 500-MHz ring oscillator circuit.

High-resolution subsurface microscopy of CMOS integrated circuits using radially polarized light

Comparison of high-resolution sub-surface microscopy shows that illumination with linear polarization resolves an edge with resolutions of 95 nm and 120 nm, depending on E-field orientation, while radial polarization achieves a resolution of 98 nm.

Measuring propagation delays of critical paths using time-resolved LADA

Laser-assisted device alteration is an established technique used to identify critical speed paths in integrated circuits. By using a synchronized pulsed laser, logic transition waveforms have been acquired that can be used to measure propagation delays of the critical path signals. A method for determining the polarity of the transitions is presented for LADA sites on bulk 28nm CMOS technology. The time-resolved LADA logic waveforms are compared to, and are in close agreement with, laser voltage probe waveforms acquired from the same device.