Terahertz nanoscopy: Advances, challenges, and the road ahead

Applied Physics Reviews, Journal Year: 2024, Volume and Issue: 11(2)

Published: April 10, 2024

Exploring nanoscale material properties through light-matter interactions is essential to unveil new phenomena and manipulate materials at the atomic level, paving way for ground-breaking advancements in nanotechnology science. Various elementary excitations low-energy modes of reside terahertz (THz) range electromagnetic spectrum (0.1–10 THz) occur over various spatial temporal scales. However, due diffraction limit, a slew THz studies are restricted drawing conclusions from spatially varying responses around half probing wavelengths, i.e., tens couple hundred micrometers. To address this fundamental challenge, scanning near-field optical microscopy (SNOM), notably scattering-type SNOM (s-SNOM), combined with sources has been employed fueling growing interest technique across multiple disciplines. This review (1) provides an overview system developments SNOM, (2) evaluates current approaches understand quantify interactions, (3) explores advances applications, especially nano-scale employing s-SNOM, (4) envisions future challenges potential development avenues practical use s-SNOM.

Language: Английский

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Direct Frequency Comb Cavity Ring-Down Spectroscopy Using Vernier Filtering

The Journal of Physical Chemistry A, Journal Year: 2025, Volume and Issue: unknown

Published: Jan. 24, 2025

We present direct frequency comb cavity ring-down spectroscopy with Vernier filtering as a straightforward approach to sensitive and multiplexed trace gas detection. The high finesse acts both extend the interaction length sample spectral filter, alleviating need for dispersive elements or an interferometer. In this demonstration, free running interband cascade laser was used generate centered at 3.3 μm covering ∼10 cm–1 (300 GHz), which coupled into high-finesse cavity, providing 0.9 km of effective path length. configuration transmitted modes in sequence, decays could be initiated either acousto-optic modulator by scanning beyond adiabatic limit, trade-offs between duty cycle sensitivity. This implementation achieved figure merit 4.3 × 10–8 Hz–1/2 per element, measurements toluene demonstrated its ability observe concentrations continuum absorber. method does not require anything conventional single-mode instrument other than optical comb, making it readily accessible wide range applications.

Language: Английский

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Shaping terahertz harmonic frequency combs with frequency-dependent external reflectors

Physical review. A/Physical review, A, Journal Year: 2025, Volume and Issue: 111(4)

Published: April 17, 2025

Language: Английский

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Bi-stability and period-doubling cascade of frequency combs in exceptional-point lasers

Nanophotonics, Journal Year: 2025, Volume and Issue: unknown

Published: May 21, 2025

Abstract Recent studies have demonstrated that a laser can self-generate frequency combs when tuned near an exceptional point (EP), where two cavity modes coalesce. These EP induce periodic modulation of the population inversion in gain medium, and their repetition rate is independent cavity’s free spectral range. In this work, we perform stability analysis reveals notable properties combs, bi-stability period-doubling cascade. The cascade enables halving while maintaining comb’s total bandwidth, presenting opportunities for design highly compact comb generators.

Language: Английский

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Mid-infrared dual-comb spectroscopy with quantum cascade lasers

APL Photonics, Journal Year: 2024, Volume and Issue: 9(3)

Published: March 1, 2024

Since its invention in 1994, the quantum cascade laser (QCL) has emerged as a versatile light source of wavelength 4–12 µm, covering most mid- and long-wavelength infrared spectral ranges. Its application range widened even further since frequency comb operation use for dual-comb spectroscopy (DCS) was demonstrated. In this tutorial, we introduce unique properties QCL combs, such high optical power, multi-GHz repetition rate, narrow linewidths. Implemented setup, allows broadband, low-noise measurements strongly absorbing samples with sub-microsecond time resolution, resolution better than 10−3 cm−1/30 MHz. The advantages DCS will be discussed context broad applications. power (both total per tooth) is leveraged aqueous solution or at large stand-off distances. Microsecond temporal address demand probing rapid protein dynamics combustion diagnostics. MHz-level turn, facilitates accurate line parameter studies low pressure cold molecular gases. Future development directions technology are discussed, including response DCS, instrument miniaturization, expansion toward THz frequencies. Overall, tutorial aims giving introduction to

Language: Английский

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Exploring frequency comb generation in optically injected ring quantum cascade lasers

Published: March 12, 2024

Quantum Cascade Lasers (QCLs) have immense potential for generating chip-scale frequency combs in the mid-infrared and terahertz spectral regions. In this work, we demonstrate formation of within ring QCLs using optical injection from a Distributed Feedback (DFB) laser. By carefully selecting DFB design that aligns with cavity modes (around 3.3 THz) employing bus waveguide light injection, show can be selectively formed controlled cavity. Numerical modeling suggests observed comb is frequency-modulated nature, acting as trigger. Furthermore, cavity's ability to function filter, feature could hold significant value photonic integrated circuits. Our findings highlight promise couplers robust approach injecting extracting radiation offer exciting possibilities generation new states domain, including waves, solitons, more.

Language: Английский

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Frequency combs induced by optical feedback and harmonic order tunability in quantum cascade lasers

APL Photonics, Journal Year: 2023, Volume and Issue: 8(11)

Published: Nov. 1, 2023

This study investigates the interaction between frequency combs and optical feedback effects in Quantum Cascade Lasers (QCLs). The theoretical analysis reveals new phenomena arising from interplay comb generation feedback. By considering bias current corresponding to free-running single mode emission, introduction of can trigger combs, including both fundamental harmonic combs. presents opportunities extend region generate with different orders through optimization external cavity parameters, such as losses length. Furthermore, this demonstrates that selectively tune order a pre-existing by adjusting length, particularly for ratios around 1%, which are readily achievable experimental setups. Under strong conditions (Acket parameter C > 4.6), mixed states emerge, displaying features laser dynamics. While is predominantly centered on terahertz QCLs, we have also confirmed described occur when utilizing mid-infrared QCL parameters. work establishes connection technology utilization feedback, providing avenues exploration advancement field. In fact, novel reported open pathway toward methodologies across various domains, design tunable sources, hyperspectral imaging, multi-mode coherent sensing, multi-channel communication.

Language: Английский

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Self-consistent simulations of intracavity terahertz comb difference frequency generation by mid-infrared quantum cascade lasers

Journal of Applied Physics, Journal Year: 2023, Volume and Issue: 133(23)

Published: June 16, 2023

Portable terahertz (THz) frequency comb sources are highly desired for applications in rotational molecular spectroscopy and sensing. To date, direct THz quantum cascade laser (QCL) generation is not achievable at room temperature. However, based on intracavity difference (DFG) mid-infrared (mid-IR) QCLs a promising alternative. Here, we present numerical study of DFG-QCL formation mid-IR self-consistent multi-domain simulation approach. The dynamical simulations performed using our open-source software tool mbsolve, which provides flexible efficient codebase solving the generalized full-wave Maxwell–Bloch equations. DFG active region dual-wavelength QCL considered radiation. mixing process and, thus, require high second-order intersubband nonlinear susceptibility can be obtained by targeted engineering. associated effects included Hamiltonian All necessary input parameters description system determined self-consistently in-house ensemble Monte Carlo stationary carrier transport simulations. Notably, such solver that does employ common rotating wave approximation, as broadband optical field extending from to investigated. Our modeling approach results two setups validated against experimental data, showing reasonable agreement. Furthermore, obtain locked modulated state regimes.

Language: Английский

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Advancing Aerospace Inspection With Terahertz Technology

Advances in mechatronics and mechanical engineering (AMME) book series, Journal Year: 2024, Volume and Issue: unknown, P. 195 - 211

Published: May 17, 2024

The chapter discusses the advancements in technology security and aerospace inspection, focusing on terahertz (THz) technology. THz, a mix of radio light waves, is used detection hazardous compounds weapons, enabling accurate chemical identification, high-bandwidth communication, imaging, material analysis. However, Terahertz Gap presents challenges, leading to development THz Photoconductive Antennas (THz-PCAs), quantum cascade lasers (QCLs), frequency combs, optical photonic oscillators (OPOs), superconducting bolometers, field-effect transistors. revolutionizing non-destructive industrial quality control aviation, space exploration, non-invasive medical imaging. Challenges include cost, size, complexity, lack standardization. This suggests reducing costs, miniaturization,

Language: Английский

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Harmonic active mode locking in terahertz quantum cascade lasers

Physical review. A/Physical review, A, Journal Year: 2023, Volume and Issue: 108(1)

Published: July 5, 2023

We present a numerical study of the active harmonic mode locking (HML) quantum cascade lasers (QCLs) in terahertz (THz) spectral range. This is recently experimentally demonstrated technique based on modulation bias current laser by radio-frequency (rf) injection, allowing for generation multiple short pulses per round-trip QCL cavity. first Fabry-P\'erot (FP) configuration, unraveling impact both intrinsic parameters and rf injection characteristics generated pulses. Our demonstrates that key parameter achievement ultrashort gain bandwidth: pushing this quantity beyond 1 THz, we reproduce second-order with duration 2.5 ps. suggests combination HML design optimized cavities providing larger gain, such as multistack regions, can allow narrow approaching picosecond limit THz QCLs. Then direct comparison experiment presented, which reveals introduction an unmodulated section cavity crucial to considerably reduce Finally, motivated recent observations high-contrast localized structures optical solitons free-running ring QCLs, investigate formation these unidirectional cavities. make comparative analysis aimed at understanding if configuration guarantee improvement performance respect FP case. find properties unidirectionality absence spatial hole burning, lead 1.5-ps pulse duration, promoting devices strong candidates

Language: Английский

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