Journal of Optics and Photonics Research

Multimodal Multiphoton Tomography with a Compact Femtosecond Fiber Laser

Karsten König — Sun, 24 Dec 2023 00:00:00 +0800

Multiphoton tomography (MPT) based on near infrared (NIR) femtosecond laser technology has become a versatile high-resolution clinical and research imaging tool. We report on multimodal MPT with the air-cooled fiber laser tomograph MPTcompact. The ultracompact passively mode-locked erbium-doped 50/80 MHz laser operating at 780 nm is directly integrated into the 360° imaging head mounted on a flexible mechanical arm. The tomograph provides optical biopsies with subcellular resolution and optical metabolic imaging capability based on two-photon autofluorescence (AF), second harmonic generation, fluorescence lifetime imaging (FLIM) by time-correlated single photon counting with 250 ps temporal resolution, reflectance confocal microscopy, and white LED light CMOS camera imaging. For the first time, NIR femtosecond laser pulses have been used on human skin to realize simultaneous one-photon confocal imaging and two-photon imaging. Most useful information is provided by the two-photon excited intratissue AF of the coenzymes NAD(P)H and flavins. The signals of both types of coenzymes can be separated by FLIM. Furthermore, the free and protein-bound forms can be distinguished by time-resolved AF detection because the protein-bound NADH has one order higher AF lifetime than free (non-bound) NADH. The tomograph contains onboard storage batteries so that it can operate for up to a few hours independently from external power supply. Applications include in vivo cancer detection and in situ evaluation of anti-aging drugs and pharmaceuticals. The tomograph MPTcompact has been successfully tested in a clinical multicenter study for the diagnosis of malignant melanoma on 100 patients with suspicious pigmented lesions. MPT has the potential to realize non-invasive high-resolution label-free in vivo histology within minutes and, therefore, to reduce the number of physically taken biopsies.

Received: 14 September 2023 | Revised: 27 November 2023 | Accepted: 12 December 2023

Conflicts of Interest
The author declares that he has no conflicts of interest to this work. The author is the founder and CEO of the company JenLab GmbH.

Data Availability Statement

Data sharing is not applicable to this article as no new data were created or analyzed in this paper. The data including the final report that supports the findings of the multicenter multiphoton skin imaging study “Mi-MulTo” are available in the European Database of Medical Devices (EUDAMED) and the German Medical Device Information and DATA Bank System (DIMDI) of the Bundesinstitut für Arzneimittel und Medizinprodukte (BfArM) under the EUDAMED number CIV-18-02-022924 at www.bfarm.de and in reference (König et al., 2021).

Investigation of Polymer-Based 1×2 All-Optical Switches at C-Band Wavelength

Md Koushik Alam, Noor Afsary, Md Zahidul Islam, Md Omar Faruk Rasel — Tue, 30 Jan 2024 00:00:00 +0800

All-optical switches play a significant role in optical communication and signal processing using purely optical signals and offer efficient high-speed data transmission over conventional switches, which rely on optic–electronic conversions. This paper demonstrates 1 × 2 all-optical switches realized with the Mach–Zehnder interferometer (MZI) and directional couplers (DCs) for next-generation high-speed computing systems. We numerically design and simulate this optical switch by using the commercially available RSoft CAD BeamPROP solver. The proposed switches leverage the combined influence of DCs to achieve precise control over switching states by demonstrating remarkable phase-shifting properties with phase differences of 4π/3 and π/2 between the MZI and DC. The optical switch exhibits excess losses (ELs) from 1.27 dB to 1.40 dB and crosstalk ranging from −13.303 dB to −11.034 dB in a wavelength range of 1.53–1.56 μm, and minimal EL and crosstalk are 1.27 dB and −13.303 dB at 1.55 μm. The proposed polymer-based 1 × 2 all-optical switches could be novel devices in high-speed data transmission for optical circuitry.

Received: 28 November 2023 | Revised: 9 January 2024 | Accepted: 18 January 2024

Conflicts of Interest

The authors declare that they have no conflicts of interest to this work.

Data Availability Statement

The data that support the findings of this study are openly available in Optica Open at https://doi.org/10.1364/opticaopen.24574615.

Characteristics Analysis of Different Photonic Crystal Fiber Lattice Structures

Lavanya Anbazhagan, P. Sudhanya, R. Jansi — Wed, 25 Oct 2023 00:00:00 +0800

This study presents a comprehensive analysis of various photonic crystal fiber (PCF) lattice structures using the Finite Element Method (FEM). PCFs have gained significant importance in various optical and communication applications due to their unique optical properties. Understanding the characteristics and optimal designs of different PCF lattice structures is crucial for their effective utilization. In this research, we explore eight distinct lattice designs, including circle, square, pentagon, hexagon, heptagon, octagon, decagon, and dodecagon. We investigate how variations in the air-filling fraction (AFF), a critical structural parameter, affect the performance of these PCF structures. The utilization of FEM allows for a detailed analysis of these lattice structures, offering insights into their behavior under different conditions. By varying the AFF, we gain valuable insights into the optimal design choices for specific applications. This research aims to provide a deeper understanding of the applicability of each PCF lattice structure. By scrutinizing their performance and characteristics, it becomes possible to distinguish which lattice structure is best suited for various optical and communication applications. The findings from this study offer significant contributions to the field of photonics, guiding researchers and engineers in selecting the most suitable PCF lattice structure for their specific applications. Understanding the structural parameters that influence PCF behavior is a key step toward optimizing the performance of optical and communication systems.

Received: 8 September 2023 | Revised: 18 October 2023 | Accepted: 19 October 2023

Conflicts of Interest

The authors declare that they have no conflicts of interest to this work.

Data Availability Statement

Data available on request from the corresponding author upon reasonable request.

Dual-Frequency Lidar for Compressed Sensing 3D Imaging Based on All-Phase Fast Fourier Transform

Xiaotian Li, Yetong Hu, Yuchen Jie, Changming Zhao, Zilong Zhang — Tue, 05 Dec 2023 00:00:00 +0800

Lidar, with its advantages of high measurement accuracy, fine angular resolution, and strong anti-interference capability, plays a pivotal role in the field of scene depth information acquisition. Traditional approaches to achieving lateral spatial resolution in imaging include raster scanning and array detectors. The former necessitates frequent scanning to acquire depth maps, resulting in time consumption and instability. The latter encounters challenges such as high dark count rates, pixel crosstalk, and excessive costs for obtaining high-resolution images using array detectors. The introduction of compressed sensing (CS) offers a novel perspective on realizing non-scanning three-dimensional imaging. In this context, we propose a novel three-dimensional imaging system that combines CS with coherent dual-frequency continuous-wave lidar and utilizes the all-phase fast Fourier transform to extract both amplitude and phase information. This system requires only M measurements, and through a reconstruction algorithm, it achieves the inversion of depth information for N-pixel scenes (M << N). Integrating cost-effective components such as digital micromirrors and single-point detectors, this affordable system accomplishes three-dimensional imaging of a single target. Notably, it significantly reduces the required number of measurements while concurrently ensuring enhanced eye safety and signal-to-noise ratio.

Received: 22 August 2023 | Revised: 20 November 2023 | Accepted: 23 November 2023

Conflicts of Interest
Zilong Zhang is an editorial board member for Journal of Optics and Photonics Research, and was not involved in the editorial review or the decision to publish this article. The authors declare that they have no conflicts of interest to this work.

Data Availability Statement

Data available on request from the corresponding author upon reasonable request.

A Multipath Approach to Self-Interference Cancellation in MIMO Rayleigh Fading Channels

Archa Chandrasenan, Joseph Zacharias — Thu, 30 Nov 2023 00:00:00 +0800

An optically enabled multipath self-interference (MSI) cancellation technique for in-band full duplex (IBFD) multiple input multiple output (MIMO) Radio over Fiber RoF systems under Rayleigh fading channels is proposed. A digitally assisted Rayleigh fading channel model generates the MSI signal. An optically tunable multipath delay lines (OTMDL) module is designed using optical delay lines and an optical attenuator for coarse and fine-tuning of time delays and amplitude matching between the locally generated reference (LR) signal and the MSI signal. The OTMDL module adjusts the LR signal to cancel the effect of MSI on the signal received through the fading channel. The concept is validated using a remote sensor node of a 3 × 3 IBFD MIMO RoF system with a Rayleigh fading channel. The system's performance is evaluated by determining the MSI cancellation depths using the OTMDL section for various cancellation channels and by computing the MSI cancellation for both single band and wideband signals across different cancellation channels. An average value of MSI cancellation depth of 20.38 dB is obtained for a single-tone radio frequency signal in the range 15–25 GHz. Thus, the proposed system for MSI cancellation can be utilized in wireless communication systems in multiple ways.

Received: 22 September 2023 | Revised: 7 November 2023 | Accepted: 10 November 2023

Conflicts of Interest
The authors declare that they have no conflicts of interest to this work.

Data Availability Statement

Data available on request from the corresponding author upon reasonable request.

Analysis of the Optical Properties and Electronic Structure of Semiconductors of the Cu2NiXS4 (X = Si, Ge, Sn) Family as New Promising Materials for Optoelectronic Devices

Dilshod Nematov — Tue, 30 Jan 2024 00:00:00 +0800

In this work, the optoelectronic characteristics of kesterites of the Cu₂NiXS₄ system (X = Si, Ge, Sn) were studied. The electronic properties of the Cu₂NiXS₄ (X = Si, Ge, Sn) system were studied using first-principles calculations within the framework of density functional theory. For calculations, ab initio codes VASP and Wien2k were used. The high-precision modified Beke-Jones (mBJ) functional and the hybrid HSE06 functional were used to estimate the bandgap, electronic, and optical properties. Calculations have shown that when replacing Si with Ge and Sn, the band gap decreases from 2.58 eV to 1.33 eV. Replacing Si with Ge and Sn reduces the overall density of electronic states. In addition, new deep (shallow) states are formed in the band gap of these crystals, which is confirmed by the behavior of their optical properties. The obtained band gap values are compared with existing experimental measurements, demonstrating good agreement between HSE06 calculations and experimental data. The nature of changes in the dielectric constant, absorption capacity, and optical conductivity of these systems depending on the photon energy has also been studied. The statistical dielectric constant and refractive index of these materials were found. The results will help increase the amount of information about the properties of the materials under study and will allow the use of these compounds in a wider range of optoelectronic devices, in particular, in solar cells and other devices that use solar radiation to generate electric current.

Received: 30 September 2023 | Revised: 9 January 2024 | Accepted: 19 January 2024

Conflicts of Interest

The author declares that he has no conflicts of interest to this work.

Data Availability Statement

Data sharing is not applicable to this article as no new data were created or analyzed in this study.