Decade-Spanning High-Precision Terahertz Frequency Comb

Finneran, Ian A.; Good, Jacob; Holland, Daniel B.; Carroll, P. Brandon; Allodi, Marco A.; Blake, Geoffrey A.

doi:10.1103/physrevlett.114.163902

Cited by 56 publications

(48 citation statements)

References 22 publications

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“…Another approach-especially for high-precision, and broadband THz spectroscopy-is dual-comb spectroscopy. [8][9][10][11][12][13][14][15] A dual-comb setup has no moving parts and in addition allows a very precise measurement of the frequency. Since in existing THz dual-comb setups the THz signal is not generated directly, they still present a wide footprint and low THz powers.…”

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confidence: 99%

“…Since in existing THz dual-comb setups the THz signal is not generated directly, they still present a wide footprint and low THz powers. 10,[13][14][15] In contrast, terahertz quantum cascade lasers (THz QCLs) are a very promising technology for applications at THz frequencies. 1,16,17 THz QCLs have the advantage that they provide much more power, operate in continuous wave (CW), and extend towards higher frequencies.…”

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On-chip, self-detected terahertz dual-comb source

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Villares

et al. 2016

Applied Physics Letters

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We present a directly generated on-chip dual-comb source at terahertz (THz) frequencies. The multi-heterodyne beating signal of two free-running THz quantum cascade laser frequency combs is measured electrically using one of the combs as a detector, fully exploiting the unique characteristics of quantum cascade active regions. Up to 30 modes can be detected corresponding to a spectral bandwidth of 630 GHz, being the available bandwidth of the dual comb configuration. The multi-heterodyne signal is used to investigate the equidistance of the comb modes showing an accuracy of 10−12 at the carrier frequency of 2.5 THz.

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On-chip, self-detected terahertz dual-comb source

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Scalari

Villares

et al. 2016

Applied Physics Letters

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“…THz QCL based FCs have the advantage overexisting THz FCs based on photoconductive emitters to provide a higher brightness in more compact form and higher efficiencies [14,15]. However, it can be envisioned that the latest development on highly efficient broadband photoconductive emitters using fiber laser as a pump source will allow in the future also compact and efficient FCs based on that technology [23,24].…”

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confidence: 99%

“…Frequency combs (FCs) have recently been reported as a tool for spectroscopic applications with QCLs [8][9][10]. So-called dual-comb spectroscopy is particularly interesting at both midinfrared and THz frequencies [11][12][13][14][15][16][17][18]. To achieve FC operation using a THz QCL, the dispersion of the laser has to be engineered to be close to 0 for the frequency range of operation [8,10].…”

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Heterogeneous terahertz quantum cascade lasers exceeding 1.9 THz spectral bandwidth and featuring dual comb operation

et al. 2017

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Abstract:We report on a heterogeneous active region design for terahertz quantum cascade laser based frequency combs. Dynamic range, spectral bandwidth and output power have been significantly improved with respect to previous designs. When individually operating the lasers, narrow and stable intermode beatnote indicate frequency comb operation up to a spectral bandwidth of 1.1 THz, while in a dispersion-dominated regime a bandwidth up to 1.94 THz at a center frequency of 3 THz can be reached. A self-detected dual-comb setup has been used to verify the frequency comb nature of the lasers.

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“…We also collected data over a 21 470 pulse window to obtain a tooth width of 3.7 kHz. 25 To conclude (Section VI), we outline near term upgrades to the system achievable via pulse compression and THz generation/detection optimization that would enable century-spanning bandwidth, that is, highresolution gas-phase spectroscopy from 0.1 to 10 THz.…”

Section: Summary Of the System Design And Performancementioning

confidence: 99%

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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Decade-Spanning High-Precision Terahertz Frequency Comb

Cited by 56 publications

References 22 publications

On-chip, self-detected terahertz dual-comb source

On-chip, self-detected terahertz dual-comb source

Heterogeneous terahertz quantum cascade lasers exceeding 1.9 THz spectral bandwidth and featuring dual comb operation

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

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