Megahertz scan rates enabled by optical sampling by repetition-rate tuning

Bajek, David; Cataluna, Maria Ana

doi:10.1038/s41598-021-02502-w

Cited by 6 publications

(1 citation statement)

References 23 publications

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“…Here, a high repetition rate of the lasers is particularly advantageous, since this reduces the demand on the sampling electronics. Examples from optical distance measurement can be directly applied to UHRR-THz-TDS systems where measurement speeds >1 MHz were realized [63], [64].…”

Section: Comparision and Outlookmentioning

confidence: 99%

THz Systems Exploiting Photonics and Communications Technologies

et al. 2023

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Terahertz (THz) systems open up the possibility of new applications of electromagnetic waves. Enormous bandwidths up to several terahertz enable the development of powerful spectroscopy systems that can provide insights into the structure and material of objects with micrometer resolution. New high power and compact THz time-domain spectroscopy (TDS) systems will be presented. The wide bandwidth also enables high-resolution imaging under far-field conditions to analyze arbitrary objects from a distance. In addition, a near-field system-on-a-chip imaging system is presented that achieves a resolution of 10 μm. Additionally, the application of terahertz waves presents challenges due to the low transmit power of the sources, high attenuation in free space, and the high noise figures of the receivers. These challenges can be overcome by antennas with high gain. Since -depending on the application -spatial scanning or focusing in a time-varying direction is required, beam steering is an essential component of many THz systems. In terms of communications, terahertz carrier frequencies offer wide bandwidths, enabling correspondingly high data rates of 100 Gbit/s and more. As a result, the frequency bands between 250 GHz and 450 GHz have already been identified and/or allocated for communication services and are being discussed as a component of 6G mobile communications. Concepts and demonstrations for 6G terahertz mobile communications will be presented. The high bandwidth of terahertz waves can also be used for high-accuracy indoor localization.INDEX TERMS THz time-domain spectroscopy, high average power THz systems, THz far-field imaging, THz near-field imaging, THz communication, THz localization, MTT 70th Anniversary Special Issue.

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Section: Comparision and Outlookmentioning

confidence: 99%

THz Systems Exploiting Photonics and Communications Technologies

et al. 2023

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Modelling optical coherence tomography for biophotonics and photobiology using an electronically tunable mode-locked laser diode

Ejidike,

Shutts,

Bajek

2024

Physics and Simulation of Optoelectronic Devices XXXII

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We propose mode-locked laser diodes (MLLDs) for their deployment in a low-cost and portable optical coherence tomography (OCT) system. OCT is an essential imaging technique used for medical diagnoses in dermatology, ophthalmology, and cardiology. Based on low-coherence interferometry, OCT directs infrared light through various layers of tissue, which is reflected onto a detector and resolved as an image. Generally, swept-source OCT (SS-OCT) systems perform better than grating based systems and time domain OCT but require expensive laser sources which are optically pumped, meaning they require an additional pump laser, limiting their deployment in clinics. To that end we propose MLLDs as an excellent candidate to realize, low-cost, compact, and portable SS-OCT enabled by their fast electronic tuning and electrically pumped, monolithic construction. We present simulated SS-OCT images using experimentally measured spectra from our InAs Quantum-Dot MLLDs and compare this to simulated data using a Thorlabs researchgrade micromechanically tuned VCSEL (vertical cavity surface emitting lasers). Our first results to date suggest MLLDs could resolve features of 62.5 µm, which, compared with the off-the-shelf system, is approximately half the resolution. Further studies suggest that by examining electronic fine-tuning of the spectral linewidths and central wavelength, MLLDs may be highlighted as a key tool in realizing low-cost portable OCT at comparable quality to existing research-grade systems. Couple this with the current shift in practices to complex image analysis using machine learning methods, a handheld SS-OCT system could be realized as a low-cost, compact and versatile tool for clinicians.

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Simplifying asynchronous optical sampling: an experimental approach toward industrial integration exploiting lock-in acquisition

Peli,

Tognazzi,

Franceschini

et al. 2024

Appl. Opt.

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Time-resolved optical spectroscopies are emerging as a go-to technique for non-destructive testing of nanomaterials. Inspecting the thermal and mechanical properties of a mesoscale device requires achieving delay times beyond the ns timescale in a nanoscopy setup, potentially in a vibration polluted environment. These requirements constitute a major challenge for traditional pump-probe techniques based on moving mechanical delay lines and lock-in detection. Asynchronous optical sampling (ASOPS) and electronically controlled optical sampling (ECOPS), avoiding any moving mechanical parts, are good alternatives. However, their detection scheme is based on fast-balanced photodiodes, which, as a technology, are not as widespread, not as developed, and lack the performance of lock-in based detection. In this study, we introduce what we believe is a novel approach that integrates ASOPS/ECOPS and lock-in detection methodologies, eliminating the necessity for a reference signal and streamlining the optical configuration. By leveraging the strengths of each technique, our approach enhances simplicity and efficiency. The scheme is first validated against standard approaches in the frame of a beam-depletion measurement in a sum frequency experiment. It is then tested in a paradigmatic case study to inspect the mechanics of a single gold nanodisk, with dimensions in the 100 nm range, nanopatterned on a sapphire substrate. These results widen the range of applicability of time-resolved optical techniques as a nano-metrology tool to industrial settings.

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Megahertz scan rates enabled by optical sampling by repetition-rate tuning

Cited by 6 publications

References 23 publications

THz Systems Exploiting Photonics and Communications Technologies

THz Systems Exploiting Photonics and Communications Technologies

Modelling optical coherence tomography for biophotonics and photobiology using an electronically tunable mode-locked laser diode

Simplifying asynchronous optical sampling: an experimental approach toward industrial integration exploiting lock-in acquisition

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