arXiv subjects

Borislav Hinkov

Publications and source records attributed to Borislav Hinkov.

6 recordsLinked to original sources

arXiv2026

Infrared photonics for healthcare: A roadmap for proactive and predictive health management

The field of infrared (IR) photonics is currently undergoing remarkable progress, moving rapidly towards practical sensing applications demanded by medical therapy and diagnostics (theranostics). The Developments can be divided into three main categories: (i) novel devices and measurement concepts including advanced updates of classical approaches that push medical sensing into the spotlight; (ii) new demonstrations of photonic integrated circuit (PIC-)based IR devices enabling highly miniaturized sensors for point-of-care application as well as medical and wellness wearables; and (iii) technologically-mature IR demonstrators that enable first medical sensing and treatment applications. This roadmap paper provides a consolidated overview of this highly dynamic and interdisciplinary research field with a focus on the major roadblocks that limit the widespread adoption of IR photonics in large-scale medical diagnostics. Special attention is given to the ambivalence between the molecular-level spectroscopic interpretation and a broader health-state assessment, highlighting the need for a common framework. Additionally, the paper discusses the critical importance of unified measurement standards, calibration protocols, and medical certification processes to ensure the validity of experimental results, reproducibility, and clinical trust, particularly when novel experimental techniques and AI algorithms are involved. Perspectives from major past and current contributors to application-oriented IR photonics will be provided.

physics.app-ph↗

arXiv2025

Electron-to-photon noise transfer in mid-infrared semiconductor lasers

Noise characteristics of state-of-the art light sources are crucial parameters in understanding their limitations towards quantum applications. This work describes a method to study the electrical noise transfer of current driver sources to the intensity noise of mid-infrared emission by commercial quantum and interband cascade lasers (QCLs and ICLs, respectively). A current driver with sub-shot electrical noise in a specific frequency range (up to 10 dB below the shot noise level) was developed for this purpose. This enables testing the performance of mid-infrared lasers when driven via such a quiet pump source. By using this novel current driver, we identify the fundamental noise of a QCL and an ICL, that is the laser intensity noise resulting solely from the internal dynamics of the laser under test. The proposed methodology allows us to retrieve the noise transfer function from current to light, showing that the main limitations in observing the quantum properties of the emitted photons come from laser excess noise and poor matching between laser and detection system in terms of bandwidth and optical power. From the analysis of the measured parameters, we highlight current technological limitations and suggest which key features should be optimized in mid-infrared systems for matching the performance required by quantum applications.

physics.optics↗

arXiv2024

Shot-noise-limited emission from interband and quantum cascade lasers

The intensity noise of a laser source represents one of the key factors limiting the ultimate sensitivity in laser-based systems for sensing and telecommunication. For advanced applications based on interferometry, the availability of a shot-noise-limited local oscillator is even more important for the effective feasibility of high-precision measurements. This is particularly crucial in quantum optics applications based on homodyne detection schemes to measure non-classical light states, such as squeezed states. This work deeply investigates and analyzes the intensity noise features of the most widely used mid-infrared semiconductor heterostructured lasers: quantum cascade and interband cascade lasers. For this purpose, a comprehensive comparison of three different continuous-wave lasers operating at room temperature around 4.5 μm wavelength is presented. First, a thorough electro-optical characterization is given, highlighting the differences and the shared common characteristics of the tested devices. Then, a detailed intensity noise analysis is reported, identifying their different noise operations with a particular reference to shot-noise-limited operations. Finally, some perspectives towards advanced applications are discussed.

physics.optics↗

arXiv2023

Mid-Infrared Ring Interband Cascade Laser: Operation at the Standard Quantum Limit

Many precision applications in the mid-infrared spectral range have strong constraints based on quantum effects that are expressed in particular noise characteristics. They limit, e.g., sensitivity and resolution of mid-infrared imaging and spectroscopic systems as well as the bit-error rate in optical free-space communication. Interband cascade lasers (ICLs) are a class of mid-infrared laser exploiting interband transitions in type-II band alignment geometry. They are currently gaining significant importance for mid-infrared applications from <3 μm to >6 μm wavelength, enabled by novel types of high-performance ICLs such as ring-cavity devices. Their noise-behavior is an important feature that still needs to be thoroughly analyzed, including its potential reduction with respect to the shot noise limit. In this work, we provide a comprehensive characterization of λ = 3.8 μm-emitting, continuous-wave ring-ICLs operating at room temperature. It is based on an in-depth study of their main physical intensity noise features, such as their bias-dependent intensity noise power spectral density (INPSD) and relative intensity noise (RIN). We obtain shot-noise-limited statistics for Fourier frequencies above 100 kHz. This is an important result for precision applications, e.g. interferometry or advanced spectroscopy, which benefit from exploiting the advantage of using such a shot-noise limited source, enhancing the setup sensitivity. Moreover, it is an important feature for novel quantum optics schemes including testing specific light states below the shot noise level, such as squeezed states.

physics.optics↗

arXiv2023

Surface Protection and Activation of Mid-IR Plasmonic Waveguides for Spectroscopy of Liquids

Liquid spectroscopy in the mid-infrared spectral range is a very powerful, yet premature technique for selective and sensitive molecule detection. Due to the lack of suitable concepts and materials for versatile miniaturized sensors, it is often still limited to bulky systems and offline analytics. Mid-infrared plasmonics is a promising field of current research for such compact and surface-sensitive structures, enabling new pathways for much-needed photonic integrated sensors. In this work, we focus on extending the concept of Ge/Au-based mid-infrared plasmonic waveguides to enable broadband liquid detection. Through the implementation of high-quality dielectric passivation layers deposited by atomic layer deposition (ALD), we cover the weak and water-soluble Ge native oxide. We show that approximately 10 nm of e.g. Al2O3 or ZrO2 can already protect the plasmonic waveguides for up to 90 min of direct water exposure. This unlocks integrated sensing schemes for broadband molecule detection based on mid-infrared plasmonics. In a proof-of-concept experiment, we further demonstrate that the ZrO2 coated waveguides can be activated by surface functionalization, allowing the selective measurement of diethyl ether at a wavelength of 9.38 μm.

physics.optics↗

arXiv2023

Advanced Mid-Infrared Plasmonic Waveguides For On-Chip Integrated Photonics

Long-wave infrared (LWIR, 8-14 um) photonics is a rapidly growing research field within the mid-IR with applications in molecular spectroscopy and optical free-space communication. LWIR-applications are often addressed using rather bulky tabletop-sized free-space optical systems, preventing advanced photonic applications such as rapid-time-scale experiments. Here, device miniaturization into photonic integrated circuits (PICs) with maintained optical capabilities is key to revolutionize mid-IR photonics. Sub-wavelength mode confinement in plasmonic structures enabled such miniaturization approaches in the visible-to-near-IR spectral range. However, adopting plasmonics for the LWIR needs suitable low-loss and -dispersion materials with compatible integration strategies to existing mid-IR technology. In this work we further unlock the field of LWIR/mid-IR PICs, by combining photolithographic patterning of organic polymers with dielectric-loaded surface plasmon polariton (DLSPP) waveguides. In particular, polyethylene shows favorable optical properties, including low refractive index and broad transparency between ~2-200 um. We investigate the whole value chain, including design, fabrication, and characterization of polyethylene-based DLSPP waveguides and demonstrate their first-time plasmonic operation and mode guiding capabilities along s-bend structures. Low bending losses of ~1.3 dB and straight-section propagation lengths of ~1 mm, pave the way for unprecedented, complex on-chip mid-IR photonic devices. Moreover, DLSPPs allow full control of the mode parameters (propagation length and guiding capabilities) for precisely addressing advanced sensing and telecommunication applications with chip-scale devices.

physics.optics↗