20 THz broadband generation using semi-insulating GaAs interdigitated photoconductive antennas

Hale, Peter John; Madéo, Julien; Chin, Chun-Chieh; Dhillon, Sukhdeep; Mangeney, J.; Tignon, Jérôme; Dani, Keshav M.

doi:10.1364/oe.22.026358

Cited by 60 publications

(42 citation statements)

References 23 publications

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“…Quantum cascade lasers [7] provide a continuous wave source tunable in this spectral window. Pulses can also be produced by photoconductive switches [8,9] or via laser-induced air plasma generation [10][11][12]. However, to obtain stable and intense electric fields combined with femtosecond temporal resolution, the workhorse approach relies on the generation of coherent field transients by frequency mixing processes in nonlinear crystals [13,14].…”

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confidence: 99%

Coherent Field Transients below 15 THz from Phase-Matched Difference Frequency Generation in 4H-SiC

Fischer

Bühler

Kurihara

et al. 2017

Conference on Lasers and Electro-Optics

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We experimentally demonstrate tunable, phase-matched difference frequency generation covering the spectral region below 15 THz using 4H-SiC as a nonlinear crystal. This material combines a non-centrosymmetric lattice and strong birefringence with broadband transparency at low optical frequencies. Thorough refractive index measurements in the terahertz spectral range allow us to calculate phase-matching conditions for any near-infrared pump laser source. 4H-SiC is also exploited as a detector crystal for electro-optic sampling. The results allow us to estimate the effective second-order nonlinear coefficient. The generation of coherent radiation in the spectral region between 5 and 15 THz is a major challenge for solid-state sources, despite its relevant interest for the study of fundamental excitations in condensed matter systems. In fact, the corresponding energy range from 20 to 60 meV includes various molecular vibrations [1][2][3], as well as optical phonons in solids [4,5] and low-energy collective modes in correlated materials such as superconductors [6]. Quantum cascade lasers [7] provide a continuous wave source tunable in this spectral window. Pulses can also be produced by photoconductive switches [8,9] or via laser-induced air plasma generation [10][11][12]. However, to obtain stable and intense electric fields combined with femtosecond temporal resolution, the workhorse approach relies on the generation of coherent field transients by frequency mixing processes in nonlinear crystals [13,14]. A typical setup is based on difference frequency generation (DFG) driven by an ultrafast laser system. Unfortunately, in the elusive spectral region between 5 and 15 THz, most nonlinear crystals applied for DFG such as GaSe, AgGaS 2 (AGS), and BBO, exhibit strong optical phonon resonances that lead to reststrahlen bands where radiation cannot penetrate into the material [see Fig. 1(a)]. In addition, isotropic materials such as ZnTe are lacking birefringence and, therefore, do not allow adjustment of phase matching. Furthermore, organic nonlinear crystals [15] show heavily structured spectra in the frequency range of interest and display inherently low damage thresholds. Recently, preliminary investigations by Naftaly et al.[16] suggested 4H-SiC as a crystal suitable for nonlinear optics in the multi-terahertz range. So far, this outstanding material has received little attention in experimental works that are limited to the demonstration of nonlinear properties in the near infrared [17], mid-infrared DFG above the optical phonon frequencies [18], and emission of 1 THz radiation from 6H-SiC [19].In this Letter, we experimentally demonstrate the application of 4H-SiC for the generation of ultrashort field transients tunable between 5 and 15 THz, and its use as an electro-optic sampling (EOS) crystal.SiC exhibits a large plurality of polymorphs with hexagonal, cubic, and rhombohedral symmetry [20]. Owing to its technological relevance, high-quality synthetic crystals of 4H-SiC are available. Its lattice, sketched in...

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confidence: 99%

Coherent Field Transients below 15 THz from Phase-Matched Difference Frequency Generation in 4H-SiC

Fischer

Bühler

Kurihara

et al. 2017

Conference on Lasers and Electro-Optics

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“…19 Further optimization of THz emission efficiency at high frequencies by implementing a reflection emitter geometry and detection by multiple inorganic crystals or poled EO sensitive polymers 35 should enable gap-free measurement of gas phase signatures to at least 10 THz, covering nearly a century of bandwidth. 11 Thus, this instrument overcomes many limitations of past THz-TDS and ASOPS-THz-TDS systems and demonstrates future paths to high precision, high dynamic range gas-phase spectroscopy covering the entire THz region.…”

Section: Discussionmentioning

confidence: 93%

“…According to Drude-Lorentz simulations of GaAs interdigitated THz emitter behavior, a pulse width of 50 fs will limit the emitter bandwidth to 12 THz and a pulse width of 100 fs will limit the emitter bandwidth to 6 THz. 11 Since we do not employ a pulse compressor, it is likely that our pump pulse width is broadened to >100 fs, leading to a lack of output above 3.5 THz. The covered bandwidth can therefore be improved in the future by compression of pump pulse width to below 50 fs to ensure emitter output up to 10 THz.…”

Section: Signal Digitization and Thz Bandwidthmentioning

confidence: 99%

“…Such a delay stage based THz-TDS system was recently demonstrated achieving an unprecedented bandwidth of ∼20 THz, but provided limited frequency resolution. 11 While simple and robust, delay stages suffer from several limitations: moving parts present a challenge in maintaining uniform alignment and focusing of the probe pulse train throughout the scan, the scan rate is limited by the speed of motors, and the length of time delay scanned is limited by the length of the stage. These limitations make achieving both Doppler-limited resolution and decade spanning bandwidth extraordinarily challenging for conventional delay stages.…”

Section: Introductionmentioning

confidence: 99%

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A decade-spanning high-resolution asynchronous optical sampling terahertz time-domain and frequency comb spectrometer

Good

Holland

Finneran

et al. 2015

Review of Scientific Instruments

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Terahertz heterodyne spectrometer using a quantum cascade laser Appl. Phys. Lett. 97, 161105 (2010) We present the design and capabilities of a high-resolution, decade-spanning ASynchronous OPtical Sampling (ASOPS)-based TeraHertz Time-Domain Spectroscopy (THz-TDS) instrument. Our system employs dual mode-locked femtosecond Ti:Sapphire oscillators with repetition rates offset locked at 100 Hz via a Phase-Locked Loop (PLL) operating at the 60th harmonic of the ∼80 MHz oscillator repetition rates. The respective time delays of the individual laser pulses are scanned across a 12.5 ns window in a laboratory scan time of 10 ms, supporting a time delay resolution as fine as 15.6 fs. The repetition rate of the pump oscillator is synchronized to a Rb frequency standard via a PLL operating at the 12th harmonic of the oscillator repetition rate, achieving milliHertz (mHz) stability. We characterize the timing jitter of the system using an air-spaced etalon, an optical cross correlator, and the phase noise spectrum of the PLL. Spectroscopic applications of ASOPS-THz-TDS are demonstrated by measuring water vapor absorption lines from 0.55 to 3.35 THz and acetonitrile absorption lines from 0.13 to 1.39 THz in a short pathlength gas cell. With 70 min of data acquisition, a 50 dB signal-to-noise ratio is achieved. The achieved root-mean-square deviation is 14.6 MHz, with a mean deviation of 11.6 MHz, for the measured water line center frequencies as compared to the JPL molecular spectroscopy database. Further, with the same instrument and data acquisition hardware, we use the ability to control the repetition rate of the pump oscillator to enable THz frequency comb spectroscopy (THz-FCS). Here, a frequency comb with a tooth width of 5 MHz is generated and used to fully resolve the pure rotational spectrum of acetonitrile with Doppler-limited precision. The oscillator repetition rate stability achieved by our PLL lock circuits enables sub-MHz tooth width generation, if desired. This instrument provides unprecedented decade-spanning, tunable resolution, from 80 MHz down to sub-MHz, and heralds a new generation of gas-phase spectroscopic tools in the THz region. C 2015 AIP Publishing LLC. [http://dx

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“…Reaching this level of precision and accuracy is significant for THz metrology, as it is the first demonstration of broadband, Doppler-limited spectroscopy in the THz region. The Ti:sapphire oscillators extend the bandwidth of the instrument to measure transitions between 1-2 THz, and can be further extended to 20 THz with proper optical pulse compression and THz emitter optimization, with no loss in fractional precision [16].…”

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confidence: 99%

Decade-Spanning High-Precision Terahertz Frequency Comb

et al. 2015

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The generation and detection of a decade-spanning terahertz (THz) frequency comb is reported using two Ti:sapphire femtosecond laser oscillators and asynchronous optical sampling THz time-domain spectroscopy. The comb extends from 0.15 to 2.4 THz, with a tooth spacing of 80 MHz, a linewidth of 3.7 kHz, and a fractional precision of 1.8 × 10 −9 . With time-domain detection of the comb, we measure three transitions of water vapor at 10 mTorr between 1-2 THz with an average Doppler-limited fractional accuracy of 6.1 × 10 −8 . Significant improvements in bandwidth, resolution, and sensitivity are possible with existing technologies.

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20 THz broadband generation using semi-insulating GaAs interdigitated photoconductive antennas

Cited by 60 publications

References 23 publications

Coherent Field Transients below 15 THz from Phase-Matched Difference Frequency Generation in 4H-SiC

Coherent Field Transients below 15 THz from Phase-Matched Difference Frequency Generation in 4H-SiC

A decade-spanning high-resolution asynchronous optical sampling terahertz time-domain and frequency comb spectrometer

Decade-Spanning High-Precision Terahertz Frequency Comb

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