Quantum emitters in two-dimensional layered hexagonal boron nitride are quickly emerging as a highly promising platform for next-generation quantum technologies. However, precise identification and control of defects are key parameters to achieve the next step in their development. We conducted a comprehensive study by analyzing over 10,000 photoluminescence emission lines, revealing 11 distinct defect families within the 1.6 to 2.2 eV energy range, challenging the hypotheses of a random energy distribution. These findings provide valuable insights to decipher the microscopic origin of emitters in hBN. The spectral spacing between defect families could serve as a key parameter for theoretical investigations We also explored the influence of hBN host morphology on defect family formation, demonstrating its crucial impact. By tuning flake size and arrangement, we achieve selective control of defect types while maintaining high spatial density. This offers a scalable approach to defect emission control, diverging from costly engineering methods.
Donor-acceptor biphenyl derivatives are particularly interesting model compounds presenting a charge transfer
absorption band because the extent of conjugation, and therefore the amount of charge transfer between the substituents,
may be varied by a controllable structural feature, namely the torsion angle between the two phenyl rings. This feature
has become even more interesting since chromophores of strong zwitterionic character, synthesized with a twist of nearly
90°, have been shown to exhibit unprecedented quadratic responses [1], over an order of magnitude above that of the
best conventional push-pull chromophores. In this context, we have investigated both experimentally and theoretically,
two biphenyl based systems with varying inter-aryl angles: a
nitro-piperidinyl series [2] of conventional push-pull
character and a pyridinium-phenoxide series [3] of zwitterionic character. The results agree qualitatively with semiempirical
simulations based on the AM1 Hamiltonian [4] used with the COSMO solvation model [5]. For the first series,
the decrease in quadratic response with increasing dihedral angle indicates that oscillator strength loss is the dominant
factor. In the second series, the corresponding increase in quadratic response points to the change in dipole moment upon
excitation as the leading effect. Here, we will analyze to what extent the more ab initio electronic structure calculations
based on the density functional theory may provide more quantitative results in spite of the problems they face in the
description of charge transfer systems.
Polymers doped with non-linear optical (NLO) molecules are key materials in the elaboration of organic NLO devices. In this field, there is an ongoing need for chromophores with large dipole moments and optical non linearities. Here, we consider pyridinium phenoxides, a type of zwitterionic biphenyl-like molecule. A combination of mathematical modelling and some preliminary experimental measurements indicate that the NLO properties of these molecules depend on the twist angle existing between the two aromatic rings. In order to corroborate this structure/activity relationship, different sterically hindered pyridinium phenoxides were synthesized using the Suzuki coupling reaction involving a boronic ester and an aryl halide. We analyze the solvatochromism of the substituted zwitterions in details, determine the chemical equilibrium of protonation and perfom nonlinear optical measurements which are interpreted with the help of semi-empirical calculations.
Nonlinear optical photopolymers are of special interest for the realization of permanent integrated optical circuits via polymerization induced by one or two-photon absorption processes. In this context, we have explored the possibilities to create integrated devices by the 1D and 3D control of the photopolymerization.
The various growth forms of self-written wave guides created in the bulk of photopolymerizable resins are presented and analyzed, both experimentally and theoretically. Under quasi-solitonic propagation conditions, the control of the refractive index during the photopolymerization progression allows the elaboration of wave guides over large distances (typically a few cm). We have also taken advantage of the high spatial selectivity of the two-photon absorption procedure for the design of controlled polymerized pathways. By using a two-photon confocal microscopy technique with a femtosecond laser source to activate the polymerization, we demonstrate how it is possible to create optical circuits in the bulk of doped photopolymers.
Moreover, the permanent freezing of the orientation of push-pull chromophores embedded in the polymeric matrices opens up the possibility to design integrated circuits with different optical functions. Thus, by combining non linear optical properties and multi-photon polymerization technique, active 3D optical devices can be created in functionalized photopolymers.
Up to now, most of the optical integrated devices are realized on glass or III-V substrates and the waveguides are usually obtained by photolithography techniques. We present here a new approach based on the use of photopolymerizable compounds. The conditions of self-written channel creation by solitonic propagation inside the bulk of these photopolymerizable formulations are analyzed. Both experimental and theoretical results of the various stages of self-written guide propagation are presented. A further step has been achieved by using a two-photon absorption process for the polymerization via a confocal microscopy technique. Combined with the solitonic guide creation, this technique allows to draw 3D optical circuits. Finally, by doping the photopolymerizable mixtures with push-pull chromophores having a controlled orientation, it will be possible to create active optical integrated devices.
A method for the investigation of the dynamics of two semiconductor lasers, grown side-by-side on the same wafer to enhance the lateral optical coupling, is presented. Using steady state analysis, parameter regimes of relevant dynamics are identified. This is completed by a spectral analysis, were two routes to chaos are implicated. Finally, we confirm the calculations by showing an avoided crossing type of behavior for the coupling strength.
A multimode model is necessary to describe the behavior observed in
a twin stripe diode laser. We will use a single-stripe version of the
device to calibrate the parameters enabling the model to be used in
the description and analysis of the twin-stripe lasers.
A novel multi-longitudinal-mode rate-equations description of the Fabry-Perot type semiconductor laser is presented. The model includes gain dynamics among the longitudinal modes due to e.g. spatial hole burning.
Our report focuses on the strong kink found in the P-I output of an asymmetric twin stripe semiconductor laser. A multi longitudinal mode model is used to describe the system. The model allows for asymmetric coupling of the two lasers and also accounts for multi longitudinal effects within and in-between the lasers.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
INSTITUTIONAL Select your institution to access the SPIE Digital Library.
PERSONAL Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.