Photonic molecules and spectral engineering

This chapter reviews the fundamental optical properties and applications of pho-tonic molecules (PMs) - photonic structures formed by electromagnetic coupling of two or more optical microcavities (photonic atoms). Controllable interaction between light and matter in photonic atoms can be further modified and en-hanced by the manipulation of their mutual coupling. Mechanical and optical tunability of PMs not only adds new functionalities to microcavity-based optical components but also paves the way for their use as testbeds for the exploration of novel physical regimes in atomic physics and quantum optics. Theoretical studies carried on for over a decade yielded novel PM designs that make possible lowering thresholds of semiconductor microlasers, producing directional light emission, achieving optically-induced transparency, and enhancing sensitivity of microcavity-based bio-, stress- and rotation-sensors. Recent advances in material science and nano-fabrication techniques make possible the realization of optimally-tuned PMs for cavity quantum electrodynamic experiments, classical and quantum information processing, and sensing.Comment: A review book chapter: 29 pages, 19 figure

Single molecule detection from a large-scale SERS-active Au79Ag21 substrate

Detecting and identifying single molecules are the ultimate goal of analytic sensitivity. Single molecule detection by surface-enhanced Raman scattering (SM-SERS) depends predominantly on SERS-active metal substrates that are usually colloidal silver fractal clusters. However, the high chemical reactivity of silver and the low reproducibility of its complicated synthesis with fractal clusters have been serious obstacles to practical applications of SERS, particularly for probing single biomolecules in extensive physiological environments. Here we report a large-scale, free standing and chemically stable SERS substrate for both resonant and nonresonant single molecule detection. Our robust substrate is made from wrinkled nanoporous Au79Ag21 films that contain a high number of electromagnetic “hot spots” with a local SERS enhancement larger than 109. This biocompatible gold-based SERS substrate with superior reproducibility, excellent chemical stability and facile synthesis promises to be an ideal candidate for a wide range of applications in life science and environment protection

Ab initio calculations of optical properties of silver clusters: cross-over from molecular to nanoscale behavior

Electronic and optical properties of silver clusters were calculated using two different \textit{ab initio} approaches: 1) based on all-electron full-potential linearized-augmented plane-wave method and 2) local basis function pseudopotential approach. Agreement is found between the two methods for small and intermediate sized clusters for which the former method is limited due to its all-electron formulation. The latter, due to non-periodic boundary conditions, is the more natural approach to simulate small clusters. The effect of cluster size is then explored using the local basis function approach. We find that as the cluster size increases, the electronic structure undergoes a transition from molecular behavior to nanoparticle behavior at a cluster size of 140 atoms (diameter $\sim 1.7$\,nm). Above this cluster size the step-like electronic structure, evident as several features in the imaginary part of the polarizability of all clusters smaller than Ag$_\mathrm{147}$, gives way to a dominant plasmon peak localized at wavelengths 350\,nm$\le\lambda\le$ 600\,nm. It is, thus, at this length-scale that the conduction electrons' collective oscillations that are responsible for plasmonic resonances begin to dominate the opto-electronic properties of silver nanoclusters

Comparion of two techniques crosslinking for progressive keratectasia

Purpose: to compare surgical approaches, features of the postoperative period and functional results of conventional and opti- mized crosslinking techniques.Methods: We followed 2 groups of patients (10 patients, 10 eyes each), treated in Volgograd branch of the S.N. Fyodorov Eye Microsurgery Clinic for kerotoconus of the II-III degree according to the conventional method (I group) and the optimized technique (II group). the optimized technique consisted of the customized excimer laser corneal deepitalization to the depth of 2/3 of the epithelial layer. Excimer laser ablation with intraoperative «on-line» pachymetry was made by means of Schwind Amaris-500 Hz (Schwind, Germany).Results: Method of the optimized crosslinking with a customized depth of excimer laser ablation required a longer period for satu- ration of the cornea with solution of riboflavin (mean 5-10 minutes). However, it was accompanied with a less severe corneal syndrome, a complete reepithelization and an earlier postoperative recovery of visual functions. Six months postoperatively a 1-2-line improve- ment of BCVA and UCVA was achieved in 19 patients (19 eyes). Decrease of cylindrical component averaged 1.2 D in the group I and 1 D in the group II. Mean refraction change in SE was 2.2 D in the group I and 2.0 D in the group II. Six months postoperatively one patient from the group II had a 1-line regression of BCVA in comparison to the preoperative level accompanied with a 10 μm corneal thinning and corneal curvature steepening by 2 D at the top of keratoconus, which was regarded as an aggravation of initial state.Conclusion: Both approaches have proved their safety and effectiveness. However, incurrence of the above-mentioned case of state deterioration calls for the further comparative studies in order to evaluate clinical effectiveness of these methods

Prognosis criteria for remission of hypercorticism after transsphenoidal endoscopic adenomectomy in patients with Cushing’s disease

The aim of the study. To assess the role of early postoperative examination in the prognosis of cd remission 1 year after TSS.Patients and methods. 101 Patients (12 men, 89 women, mean age 41,2 years (15-72) with confirmed cd were included. Midnight and morning serum cortisol and plasma ACTH, late night salivary cortisol, 24-h urinary free cortisol (ufc) excretion were performed at the days 2-3 and 12-14 after the TSS. Hypercortisolism remission status was estimated one year after surgery. The optimal threshold values of ACTH and cortisol parameters at 2-3 and 12-14 days after surgery to prediction of cd remission after TSS were calculated by roc-analysis.Results. One year after surgery cd remission was confirmed in 63 patients, whereas in 38 patients hypercortisolism persisted. Postoperative parameters of cortisol and ACTH secretion had comparable high specificity and sensitivity at 2-3 and 12-14 days after surgery for prediction cd remission.Conclusion. According to our data, morning serum cortisol ≤388 nmol/l and plasma ACTH ≤20 pg/ml at 2-3 d after TSS may be used as a prognostic criterion for cd remission 1 year after surgery with sensitivity and specificity 94,9%, 75,9% and 83,3%, 95,8%, respectively

Efficacy of intravitreal injection of Lucentis in the treatment of diffuse diabetic macular edema associated with pan-retinal photocoagulation in proliferative diabetic retinopathy

Purpose. To evaluate the efficacy of intravitreal injection of Lucentis in the treatment of diffuse diabetic macular edema (DME) associated with pan-retinal photocoagulation in the proliferative diabetic retinopathy (DR).Material and methods. A retrospective study (58 eyes) with a high diffuse DME and proliferative DR was performed in 46 patients with insulin-dependent diabetes mellitus aged 45-73 years (mean age: 59.2±0.9 years). All participants underwent i ntravitreal injection (IVI) of Lucentis pars plana. The pan-retinal photocoagulation (PRPC) stage was performed 2 weeks after each Lucentis IVI. The main criteria were the dynamics of best corrected visual acuity (BCVA), the OCT parameters – in the central retinal thickness (1mm) area and volume of the macula. The treatment efficacy was assessed one month after the final PRPC stage.Results and discussion. At the end of treatment an increase in the average BCVA values from 0.32 to 0.45, a decrease in retinal thickness in fovea zone – from 506.9mm to 394.6mm, in the volume of macula from 12.9 to 11.6mm3 were noted. Stabilization or an increase in initial visual acuity was observed in 83.4%. The initial thickness of the retina in the region of 1mm was reduced from 506.9mm to 394.6mm, i.e. decreased by an average of 22%. The stabilization of visual functions was achieved more than in 80% of cases one month after the combi ned treatment.Conclusions. The performed retrospective study showed an efficacy of intravitreal injection of Lucentis to stabilize visual functions, to reduce the height of macular edema during the pan-retinal photocoagulation in patients with proliferative diabetic retinopathy