Scott E. Irvine

Strong-field plasmonic electron acceleration with few-cycle, phase-stabilized laser pulses

We carried out experimental investigations on surface plasmon enhanced electron acceleration with few-cycle, carrier-envelope phase (CEP) stabilized laser pulses. We determined the spectrum of electrons accelerated in the plasmonic field and found that signatures of the phase stabilized optical waveform driving the individual electron trajectories are washed out in the electron spectra. We attribute this effect to nanoscale surface roughness of the metallic samples, as supported by extensive numerical simulations. This finding explains the previously observed, low CEP sensitivity of photoemission processes from metallic films and enables the development of femtosecond electron sources for ultrafast time-resolved applications.

A gigahertz surface magneto-plasmon optical modulator

We propose a novel high-speed magnetooptic (MO) modulator based on the optical excitation of surface magneto-plasmon (SMP) waves in bismuth-substituted yttrium iron garnet (Bi-YIG). A model describing magnetization dynamics of the Bi-YIG film is used in conjunction with an SMP reflectivity model to evaluate the performance of the device. In developing the reflectivity model, the dispersion relation for the SMP waves at a Bi-YIG-metal interface is derived. The optical response of the device is modeled for various driving pulses, and the performance of the device is discussed in terms of response time, efficiency, and bandwidth. Using practical material parameters, it is found that the modulator has an improved efficiency over MO modulation devices relying on bulk propagation for comparable driving current pulse durations, as well as the added benefits of a miniature design, multigigahertz operation, and tunable bandwidth. The analysis presented here provides a useful framework for the design and development of magneto-plasmon photonic devices.

Observation of few-cycle, strong-field phenomena in surface plasmon fields

We present experimental evidence of the generation of few-cycle propagating surface plasmon polariton (SPP) wavepackets. Ultrashort plasmonic pulses were generated by few-cycle laser pulses of 5.5 fs to 6.5 fs duration on a thin silver film of 50 nm thickness coated on the face of a right-angle prism to enable Kretschmann-type SPP coupling. SPP pulses were characterized by an autocorrelation-type measurement based on fourth order, nonlinear electron photoemission induced by the SPP field. The evaluation of the measured ultrashort, fringe-resolved autocorrelation curve of the SPP wavepacket (Fig. 1a) resulted in a retrieved SPP pulse length of 6.5 fs, as evidenced by the reconstructed curve in Fig. 1b. This first demonstration of the generation of few-cycle propagating SPP wavepackets on a metal surface has important applications in ultrafast plasmonics.

Modeling of high-speed magnetooptic beam deflection

We propose a magnetooptic (MO) deflector based on a thin-film iron garnet material that operates in the gigahertz regime. The Landau-Lifshitz equation, which governs magnetization dynamics, is combined with a beam-propagation method (BPM) to evaluate the performance of the proposed device. Using practical material parameters, a deflection efficiency of 20% is predicted. Diffraction effects and temporal response are discussed and illustrated using a quasi-time-dependent BPM. This theoretical framework is not only useful for the demonstration of the MO beam deflector, but it is also practical in the design and optimization of other magnetophotonic devices.

Generation of 2 keV, 30 fs electron pulses via surface plasmon waves

We report on the generation of 2 keV, 30-fs electron pulses using laser pulses from a multipass Ti:Sapphire amplifier. This work is complemented with test particle code based on the finite-difference time-domain method.

Surface plasmon assisted 26 fs, 0.4 keV electron pulse generation

We report on the generation of 0.4 keV, 26-fs electron pulses using laser pulses from a low-intensity, 80 MHz repetition rate, Ti:Sapphire oscillator. This work is complemented with particle simulations using the finite-difference time-domain method.

Parametric excitation of spin waves in bismuth-substituted yttrium iron garnet films using the first-order Suhl instability

The first-order Suhl instability in a bismuth-substituted yttrium iron garnet (Bi-YIG) film is parametrically driven at the difference frequency of two microwave oscillators. Our results show that the onset of the instability occurs at lower threshold power when excited parametrically, and the power of the instability can be fed into other spin wave modes. Other nonlinear processes are also enhanced using parametric excitation.

Broadband optical modulation using magneto-optic Bi-YIG thin films

We present a tunable wideband bismuth-substituted yttrium iron garnet (Bi-YIG) waveguide magnieto-optic (MO) modulator. An 800 nm optical beam is modulated through active control of the magnetization of the Bi-YIG film. Large bandwidth optical modulation is achieved by driving the device in a non-resonant mode that is well below the ferromagnetic resonance frequency of the film. The MO modulator is capable of operating at bandwidths higher than 1 GHz by tuning the applied static magnetic field.

Polarization-selective optical beam deflection using magnetically activated Bi-YIG films

We demonstrate a high-speed magneto-optic (MO) beam deflector baseo n iron garnet materials. In this design, the two films are dynamically activated by external magnetic fields to achieve the necessary phase shift to enable beam deflection. Using standard material parameters, a deflection efficiency of 20% is predicted at an operating frequency of 1.0 GHz. Diffraction effects and temporal response are discussed and illustated using a quasi-time-dependent beam propagation method. This theoretical framework is not only useful for the demonstration of the MO beam deflector, but it is also applicable in the design and optimization of other magneto-photonic devices.