In this report, we give a deeper investigation of the loss-compensated recirculating delayed self-heterodyne interferometer (LC-RDSHI) for ultra-narrow linewidth measurement, including the theoretical analysis, experimental implementation, further modification on the system and more applications. Recently, less than 1kHz linewidth fiber lasers have been commercialized. But even the manufacturers face a challenge on accurately measuring the linewidth of such lasers. There is a need to develop more accurate methods to characterize ultra-narrow laser linewidth and frequency noises. Compared with other currently available linewidth measurement techniques, the loss-compensated recirculating delayed-heterodyne interferometer (LC-RDSHI) technique is the most promising one. It overcomes the bottle-neck of the high resolution requirement on the delayed self-heterodyne interferometer (DSHI) by using a short length of fiber delay line. This method does not need another narrower and more stable laser as the reference which is the necessary component in heterodyne detection. The laser spectral lineshape can be observed directly instead of complicated interpretation in frequency discriminator techniques. The theoretical analysis of a LC-RDSHI gives us a guidance on choosing the optimal parameters of the system and assists us to interpret the recorded spectral lineshape. Laser linewidth as narrow as 700Hz has been proved to be measurable by using the LC-RDSHI method. The non-linear curve fitting of Voigt lineshape to separate Lorentzian and Gaussian components was investigated. Voigt curve fitting results give us a clear view on laser frequency noises and laser linewidth nature. It is also shown that for a ultra-narrow linewidth laser, simply taking 20dB down from the maximum value of the beat spectrum and dividing by $2\sqrt{99}$ will over estimate the laser linewidth and coherent length. Besides laser linewidth measurement in the frequency domain, we also implemented time-domain frequency noise measurement by using a LC-RDSHI. The long fiber delay obtained by a fiber recirculating loop provides a higher resolution of frequency noise measurement. However, spectral width broadening due to fiber nonlinearity, environmental perturbations and laser intrinsic 1/f frequency noises are still potential problems in the LC-RDSHI method. A new method by adding a transmitter switch and a loop switch is proposed to minimize the Kerr effect caused by multiple recirculation. / Ph. D.

No description available.

This work uses the photonic filtering properties of Fabry-Perot etalons to show improvements in the electrical signals created upon photodetection of the optical signal. First, a method of delay measurement is described which uses multi-heterodyne detection to find correlations in white light signals at 20 km of delay to sub millimeter resolution. By filtering incoming white light with a Fabry-Perot etalon, the pseudo periodic signal is suitable for measurement by combining and photodetecting it with an optical frequency comb. In this way, optical data from a large bandwidth can be downconverted and sampled on low frequency electronics. Second, a high finesse etalon is used as a photonic filter inside an optoelectronic oscillator (OEO). The etalon's narrow filter function allows the OEO loop length to be extremely long for a high oscillator quality factor while still suppressing unwanted modes below the noise floor. The periodic nature of the etalon allows it to be used to generate a wide range of microwave and millimeter wave tones without degradation of the RF signal.

Nous avons développé un récepteur hétérodyne terahertz (THz) compact et ultra-sensible à base de laser à cascade quantique (QCL) comme oscillateur local et de bolomètre à électron chaud (HEB) comme mélangeur. Le récepteur est basé sur un nouveau concept pour le couplage quasi-optique entre l'oscillateur local et le mélangeur ce qui a permis de ne pas utiliser de lame semi-réfléchissante pour la superposition du signal provenant du QCL et du signal à détecter. Le mélangeur utilisé est un HEB en nitrure de niobium avec une antenne planaire formée d’une double hélice log-spiral. Le HEB est monté sur la partie plane d’une lentille convexe en silicium. L’oscillateur local est un QCL que nous avons développé avec un système de contre-réaction répartie du troisième ordre avec une faible dissipation thermique, un faisceau peu divergent et un fonctionnement mono-mode à la fréquence cible de 2.7 THz. Le couplage entre l’oscillateur local et le mélangeur HEB a également été amélioré en couplant le QCL avec une fibre creuse en diélectrique ce qui a permis d’améliorer la directivité du faisceau laser à 55 dBi. Grâce aux précédents résultats, nous avons obtenu un récepteur THz hétérodyne compact qui présente une sensibilité proche de l’état de l’art à 2.7 THz. / We demonstrate an ultra-compact Terahertz (THz) heterodyne detec- tion system based on a quantum cas- cade laser (QCL) as local oscillator and a hot electron bolometer (HEB) for the mixing. It relies on a new opti- cal coupling scheme where the local oscillator signal is coupled through the air side of the planar HEB an- tenna, while the signal to be de- tected is coupled to the HEB through the lens. This technique allows us to suppress the beam splitter usu- ally employed for heterodyne mea- surements. The mixer is a Niobium Nitride HEB with a log-spiral planar antenna on silicon and mounted on the back of a plano-convex silicon lens. We have developed a low power consumption and low beam di- vergence 3rd-order distributed feed- back laser with single mode emis- sion at the target frequency of 2.7 THz to be used as local oscillator for the heterodyne receiver. The cou- pling between the QC laser and the the HEB has been further optimized, using a dielectric hollow waveguide that reliably increases the laser beam directivity up to 55 dBi. Upon the high beam quality, sufficient output power in a single mode at the tar- geted frequency and low power dissi- pation of our local oscillator, we have build an ultra compact THz hetero- dyne receiver with sensitivity close to the state of the art at 2.7 THz.

The diploma work deals with techniques of optical contactless distance and velocity measurement. A basic summary of the methods are involved. The problematic of interferometric methods for vibration measurements is analysed in detail. It contains division of interferometers, description of their function principles and also chapters dealing with elements used in interferometers such as lasers, photodetectors and elements in the ray optical way - polarizers, retarders, optical isolators. The vibration and length measurement methods are described, as well as the conception of homodyne and heterodyne detection. Part of this work focuses on the quadrature signal processing and on the proposal of algorithm for demodulation of velocity/displacement and undergoing simple motioning object deviation. This algorithm is implemented in Labview and the whole software instrument served also for visualisation of measured data of the interferometer model constructed in the laboratory. The way how to build up a model, its setting and two possible configurations suitable for homodyne detection are described. Model of interferometer is built-up on the optical breadboard. Particular components are fixed by the help of mounts. The model and software enable to measure the velocity and the vibration deviation with the light wavelength exactness. Functionality and the exactness of the laboratory model are verified by vibrometer. Effects on the measurement uncertainty are discussed here and ways how to restrain them are proposed.

<div>Biological dynamics have been studied by many methods. Fluorescence dynamic microscopy and optical coherence tomography provided fundamental understandings of biological systems. However, their high NA optics only represent local characteristics. Biodynamic imaging (BDI) technique implements a low NA optics and acquires the statistical average of Doppler shifts that occurred by dynamic light scattering with biological dynamic subsystems provided globally averaged dynamic characteristics. </div><div>BDI is used for this study to investigate biomedical applications. The chemotherapy efficacy measurement by BDI demonstrated a good agreement between the Doppler spectral phenotypes and the preclinical outcomes. Also, dynamic responses of microbiomes by chemical stimuli demonstrated featured Doppler characteristics. The bacterial infection of epithelial spheroids showed consistent spectral responses and antibiotic-resistant E. coli infection treatment with a sensitive and resistive antibiotic showed a dramatic contrast. Furthermore, the phase-sensitive characteristics of BDI provided a clue to understanding the characteristics of the random process of biological systems. Levy-like heavy-tailed probability density functions are demonstrated and </div><div>the shape changed by infection will be discussed. </div>

Surface Plasmon Polaritons (SPPs) are considered to be attractive components for plasmonics and nanophotonic devices due to their sensitivity to interface changes, and their ability to guide and confine light beyond the diffraction limit. They have been utilized in SPP resonance sensors and near field imaging techniques and, more recently, SPP experiments to monitor and control ultrafast charge carrier and energy relaxation dynamics in thin films. In this thesis, we discuss excitation and propagation properties of ultrafast SPPs on thin extended metal films and SPP waveguide structures. In addition, localized and propagating surface plasmon interactions in functional plasmonic nanostructures will also be addressed. For the excitation studies of ultrafast SPPs, we have done detailed analysis of femtosecond surface plasmon pulse generation under resonant excitation condition using prism coupling technique. Our results show that photon-SPP coupling is a resonant process with a finite spectral bandwidth that causes spectral phase shift and narrowing of the SPP pulse spectrum. Both effects result in temporal pulse broadening and, therefore, set a lower limit on the duration of ultrafast SPP pulses. These findings are necessary for the successful integration of plasmonic components into high-speed SPP circuits and time-resolved SPP sensors. To demonstrate interactions between localized and propagating surface plasmons, we used block-copolymer based self assembly techniques to deposit long range ordered gold nanoparticle arrays onto silver thin films to fabricate composite nanoparticle thin film structures. We demonstrate that these gold nanoparticle arrays interact with SPPs that propagate at the film/nanoparticle interface and therefore, modify the dispersion relation of SPPs and lead to strong field localizations. These results are important and advantageous for plasmonic device applications. For the propagation studies of ultrafast SPPs, we have designed and constructed a home-built femtosecond photon scanning tunneling microscope (fsPSTM) to visualize ultrafast SPPs in photonic devices based on metal nanostructures. Temporal and phase information have been obtained by incorporating the fsPSTM into one arm of a Mach-Zehnder interferometer, allowing heterodyne detection. Understanding plasmon propagation in metal nanostructures is a requirement for implementing such structures into opto-electronic and telecommunication technologies.

No description available.

Yes / Satellite QKD/FSO systems, which facilitate quantum key distribution (QKD) over free-space optical (FSO) links between satellites and ground stations, present a promising pathway toward achieving global security in upcoming sixth-generation (6G) wireless communications. Our study focuses on a superior type of these systems, the satellite EB/CV-QKD/FSO, which utilizes the continuous-variable (CV) method for quantum state representation and the entanglement-based (EB) scheme for QKD implementation. We propose the use of optical phase-shift keying (QPSK) signaling and dual-threshold/heterodyne detection (DT/HD) receivers to bolster the reliability and feasibility of satellite EB/CV-QKD/FSO systems. Closed-form expressions for key system performance metrics are derived using improved channel modeling. Numerical results are presented to showcase the effects of channel impairments on the system performance. We also provide recommendations for optimal system setup parameters, aiming to enhance performance. / Ministry of Information and Communications (Vietnam) (Grant Number: DT.26/23). Asia Pacific Network Information Centre (APNIC) Foundation under the Switch! Project

In the quest for ultrathin materials compatible with CMOS technology for all-optical signal processing applications in integrated photonics, graphene appears to be a promising candidate, with broadband1 optical properties and a high and broadband optical nonlinearity. However, researchers do not agree on the value of its nonlinear refractive index, and commonly used characterization methods do not provide a clear picture of the optical nonlinearity, in terms of its tensor nature or relaxation time. In the first part of this thesis, apart from the previously used Z-scan method, we have also used the ultrafast Optical Kerr Effect method coupled to Optical Heterodyne Detection (OHD-OKE) for the characterization of the third order optical nonlinearity of monolayer CVD graphene at telecom wavelengths. This method allows to separately measure the real and the imaginary part of the third-order nonlinearity, as well as their dynamics. With respect to the Z-scan method, OHD-OKE presents the major advantage of being robust against inhomogeneities of the sample. As such, we have demonstrated that graphene has a negative nonlinear refractive index, contrary to previously reported results. In addition, we have studied the real and imaginary part of graphene’s nonlinearity, when electrostatic gating is applied to change the chemical potential of graphene. Furthermore, we have proposed an enhanced version of the OHD-OKE method, together with the appropriate theoretical framework, in order to extract the tensor elements of the nonlinearity including the out-of-plane tensor elements. In particular, we have measured separately the time response of the two main tensor elements of the nonlinear susceptibility and we have experimentally verified that the out-of-plane tensor components are negligible. In the second part of this thesis, we have investigated, from an experimental point of view, the use of the nonlinear optical response of graphene for all-optical switching applications in integrated photonics. Namely, we have designed simple silicon nitride waveguide structures that constitute basic building blocks of switching devices, which were then fabricated and covered by graphene patches. Finally, we have experimentally tested the graphene-covered structures at low and high power levels and discussed the results. / Doctorat en Sciences de l'ingénieur et technologie / info:eu-repo/semantics/nonPublished