The effect of the EXOPULSE Mollii Suit on pain and fibromyalgia-related symptoms-A randomized sham-controlled crossover trial.

BACKGROUND: Fibromyalgia pain and related symptoms are poorly managed by approved pharmacological and alternative interventions. This trial aimed to evaluate the effects of the EXOPULSE Mollii Suit-a multisite transcutaneous electrical nerve stimulation device-on fibromyalgia pain, fatigue, affective symptoms, disease impact, and quality of life. METHODS: Adult patients with fibromyalgia were enrolled. Phase 1 implied a randomized, sham-controlled, cross-over, double-blind trial, applying daily 1 h sessions of active or sham intervention, over 2 weeks (2-week washout). In the open-label phase 2, all patients received daily active intervention for 4 weeks. Comparisons on pain, fatigue, disease impact, affective symptoms, quality of life, clinical impression, and comfort ratings were performed using Friedman, Wilcoxon signed rank, and Chi2 tests. RESULTS: Thirty-three patients completed the study (93.9% female, mean age: 51.3 years). Pain (primary endpoint assessed via a visual analog scale) was significantly reduced after the active (pre-active: 6.9 ± 1.4, post-active: 5.9 ± 1.8, pre-sham: 6.8 ± 1.4, post-sham: 6.6 ± 1.5) versus the sham intervention (X2 = 10.60, p = 0.014). This was also the case of other secondary endpoints (i.e., fatigue, anxiety, and disease impact), except depression and quality of life. The Clinical Global Impression of Change (CGI-C) was significantly different between the active and sham intervention periods (X2 p = 0.035), and the different proportions of categories were as follows: 'worsening' (sham: 18.2% vs. active: 0.0%), 'improvement' (sham: 48.5% vs. active 63.6%) or 'no change (sham: 33.3% vs. active 36.4%) respectively. After phase 2, significant positive effects were observed for most of the outcomes, and 78.8% of patients reported improvement according to CGI-C. CONCLUSIONS: This study suggests the clinical benefits of the EXOPULSE Mollii Suit in alleviating pain and fibromyalgia-related fatigue, emotional symptoms, and disease impact. It is worth noting that the study has several limitations related to the low number of participants, the short-term analysis of effects in the first blinded and controlled phase, and the open-label nature of phase 2. Future studies with a larger cohort and longer protocol treatment are needed, to further confirm the current results, and evaluate the long-term effects of this technique. SIGNIFICANCE: Patients with fibromyalgia suffer from pain as well as fatigue, sleep impairment, emotional disturbances, and altered quality of life. Transcutaneous electrical nerve stimulation might help manage those symptoms, but the available systems are limited by the fact that they could be applied at best over two sites. This randomized controlled study is the first to apply a multi-site transcutaneous electrical nerve stimulation device, the EXOPULSE Mollii Suit, with significant effects on fibromyalgia pain and related symptoms.

Impact of textured surfaces on the orthostatic balance of patients with multiple sclerosis.

OBJECTIVE: To perform posturographic measurements with eyes open or closed using floor coverings with different textured surfaces to study postural control in patients with multiple sclerosis (MS). METHODS: Static posturographic recordings were performed with eyes open and eyes closed on a forceplate with no covering (control condition) or covered by a textured mat with small pimples (height 2 mm) or large pimples (height 7 mm). Several posturographic variables were measured, focusing on displacements of the center of pressure (CoP) including the average velocity (Vav), the total length (L) of all displacements, and the surface (S) of the confidence ellipse. The recordings made with the textured mats were compared to the control condition with eyes open or closed. Then, the differences between the recordings made with large vs. small pimples on the one hand, and with eyes closed vs. open were calculated to assess the impact of pimple height or eye closure on posturographic measurements. Clinical assessment was based on the Expanded Disability Status Scale (EDSS) and its functional system (FS) subscores, the Modified Fatigue Impact Scale (MFIS), the Unipodal Stance test (UST), and the Timed Up-and-Go test (TUG). RESULTS: Forty-six MS patients (mean EDSS score: 3.6) completed the study. Several posturographic variables, including Vav and L, deteriorated when measured on a textured mat, especially with large pimples and in eyes open condition. In contrast, no difference was found with small pimples and eyes closed, as compared to the control condition (no covering). The deleterious impact of pimple height on posturography correlated positively with the alteration of balance and gait clinically assessed by the UST and the TUG, and also with the MFIS physical and cerebral EDSS-FS subscores, and negatively with the cerebellar and brainstem subscores. On the other hand, the impact of eye closure on posturography was negatively correlated with the visual EDSS-FS subscore. DISCUSSION: Static posturographic measurements made with different textured surfaces and visual conditions can be considered as a sensitive tool to measure "proprioceptive reserves". Actually, when cerebellar, brainstem, or visual functions are impaired, the resources of the sensory (proprioceptive) system, if preserved, can be recruited at a higher level and compensate for dysfunctions of other postural controls to maintain a satisfactory balance. In addition, this procedure of static posturographic examination can provide objective measurements correlated with clinical testing of balance and gait and could usefully complement EDSS scoring to assess disability affecting postural control and the risk of falling in MS patients.

Neural Correlates of Pain-Autonomic Coupling in Patients With Complex Regional Pain Syndrome Treated by Repetitive Transcranial Magnetic Stimulation of the Motor Cortex.

OBJECTIVES: Complex regional pain syndrome (CRPS) is a chronic pain condition involving autonomic dysregulation. In this study, we report the results of an ancillary study to a larger clinical trial investigating the treatment of CRPS by neuromodulation. This ancillary study, based on functional magnetic resonance imaging (fMRI), evaluated the neural correlates of pain in patients with CRPS in relation to the sympathetic nervous system and for its potential relief after repetitive transcranial magnetic stimulation of the motor cortex. MATERIALS AND METHODS: Eleven patients with CRPS at one limb (six women, five men, aged 52.0 ± 9.6 years) were assessed before and one month after the end of a five-month repetitive transcranial magnetic stimulation (rTMS) therapy targeting the motor cortex contralateral to the painful limb, by means of electrochemical skin conductance (ESC) measurement, daily pain intensity scores on a visual numerical scale (VNS), and fMRI with motor tasks (alternation of finger movements and rest). The fMRI scans were analyzed voxelwise using ESC and VNS pain score as regressors to derive their neural correlates. The criterion of response to rTMS therapy was defined as ≥30% reduction in VNS pain score one month after treatment compared with baseline. RESULTS: At baseline, ESC values were reduced in the affected limb vs the nonaffected limb. There was a covariance of VNS with brain activation in a small region of the primary somatosensory cortex (S1) contralateral to the painful side on fMRI investigation. After rTMS therapy on motor cortex related to the painful limb, the VNS pain scores significantly decreased by 22% on average. The criterion of response was met in six of 11 patients (55%). In these responders, at one month after treatment, ESC value increased and returned to normal in the CRPS-affected limb, and overall, the increase in ESC correlated with the decrease in VNS after motor cortex rTMS therapy. At one month after treatment, there also was a covariance of both variables (ESC and VNS) with fMRI activation of the S1 region previously mentioned. The fMRI activation of other brain regions (middle frontal gyrus and temporo-parietal junction) showed correlation with ESC values before and after treatment. Finally, we found a positive correlation at one month after treatment (not at baseline) between VNS pain score and fMRI activation in the temporo-parietal junction contralateral to painful side. CONCLUSIONS: This study first shows a functional pain-autonomic coupling in patients with CRPS, which could involve a specific S1 region. However, the modulation of sympathetic sudomotor activities expressed by ESC changes was rather correlated with functional changes in other brain regions. Finally, the pain relief observed at one month after rTMS treatment was associated with a reduced activation of the temporo-parietal junction on the side in which rTMS was performed. These findings open perspectives to define new targets or biomarkers for using rTMS to treat CRPS-associated pain. CLINICAL TRIAL REGISTRATION: The Clinicaltrials.gov registration number for the study is NCT02817880.

Shaping the spectral correlation of bi-photon quantum frequency combs by multi-frequency excitation of an SOI integrated nonlinear resonator.

We reveal the generation of a broadband (> 1.9 THz) bi-photon quantum frequency comb (QFC) in a silicon-on-insulator (SOI) Fabry-Pérot micro-cavity and the control of its spectral correlation properties. Correlated photon pairs are generated through three spontaneous four-wave mixing (SFWM) processes by using a co-polarized bi-chromatic coherent input with power P1 and P2 on adjacent resonances of the nonlinear cavity. Adjusting the spectral power ratio r = P1/(P1 + P2) allows control over the influence of each process leading to an enhancement of the overall photon pair generation rate (PGR) µ(r) by a maximal factor of µ(r = 0.5)/µ(r = 0) ≈ 1.5, compared to the overall PGR provided by a single-pump configuration with the same power budget. We demonstrate that the efficiency aND of the non-degenerate excitation SFWM process (NDP) doubles the efficiency a1 ≈ a2 of the degenerate excitation SFWM processes (DP), showing a good agreement with the provided model.

High-confinement alumina waveguides with sub-dB/cm propagation losses at 450 nm.

Amorphous alumina is highly transparent across the visible spectrum, making it a promising candidate for low-loss waveguiding at short wavelengths. However, previous alumina waveguide demonstrations in the visible region have focused on low- to moderate-confinement waveguides, where the diffuse mode reduces the design flexibility and integration density of photonic integrated circuits. Here, we have developed a high-quality etch mask and a highly selective BCl3 plasma etch, allowing etching of amorphous alumina waveguides up to 800 nm thick. Using this process, we have fabricated waveguides using an alumina film grown by atomic layer deposition (ALD) which are the lowest-loss high-confinement waveguides for blue light to date: we achieve single-mode propagation losses of 0.8 dB/cm at a propagation wavelength of 450 nm.

Impact of five floor coverings on the orthostatic balance of healthy subjects.

Plantar skin sensitivity contributes to the regulation of postural control and, therefore, changing the characteristics of the plantar support surface can modify this control. This study aimed at assessing the impact of five different floor coverings on the orthostatic balance in 48 healthy subjects. Static posturography was performed with eyes open or closed on a platform in a control condition (no covering) and with five different covering surfaces: foam, silicone, ethyl vinyl acetate, and two textured mats with small (height 2 mm) or large pimples (7 mm). The average velocity of center of pressure (CoP) displacement was the primary endpoint measure and ten other posturographic variables were assessed. Comfort and pain produced by the covering were also scored. In eyes open condition, the average velocity of CoP displacement was increased when subjects stood on the foam mat, the silicone mat, and especially the textured mat with large pimples. Several other posturographic variables showed significant changes with different types of floor coverings with eyes open. These changes were not correlated to the comfort or pain scores associated with the different surfaces. In contrast, no difference was observed compared to the control condition (no covering) with eyes closed. This study shows that adding smooth or textured floor covering can alter balance in eyes open condition. In eyes closed condition, although more disturbing for balance, healthy subjects achieved better postural adaptation, probably by mobilizing more of their proprioceptive resources. This posturographic examination procedure could, therefore, be used to assess "proprioceptive reserve" capacities in clinical practice.

Long-term analgesic effect of trans-spinal direct current stimulation compared to non-invasive motor cortex stimulation in complex regional pain syndrome.

The aim of the present study was to compare the analgesic effect of motor cortex stimulation using high-frequency repetitive transcranial magnetic stimulation or transcranial direct current stimulation and transcutaneous spinal direct current stimulation in patients with complex regional pain syndrome. Thirty-three patients with complex regional pain syndrome were randomized to one of the three treatment groups (repetitive transcranial magnetic stimulation, n = 11; transcranial direct current stimulation, n = 10; transcutaneous spinal direct current stimulation, n = 12) and received a series of 12 sessions of stimulation for 3 weeks (induction phase) and 11 sessions for 4 months (maintenance therapy). The primary end-point was the mean pain intensity assessed weekly with a visual numerical scale during the month prior to treatment (baseline), the 5-month stimulation period and 1 month after the treatment. The weekly visual numerical scale pain score was significantly reduced at all time points compared to baseline in the transcutaneous spinal direct current stimulation group, at the last two time points in the repetitive transcranial magnetic stimulation group (end of the 5-month stimulation period and 1 month later), but at no time point in the transcranial direct current stimulation group. A significant pain relief was observed at the end of induction phase using transcutaneous spinal direct current stimulation compared to repetitive transcranial magnetic stimulation (P = 0.008) and to transcranial direct current stimulation (P = 0.003). In this trial, transcutaneous spinal direct current stimulation was more efficient to relieve pain in patients with complex regional pain syndrome compared to motor cortex stimulation techniques (repetitive transcranial magnetic stimulation, transcranial direct current stimulation). This efficacy was found during the induction phase and was maintained thereafter. This study warrants further investigation to confirm the potentiality of transcutaneous spinal direct current stimulation as a therapeutic option in complex regional pain syndrome.

Neuropathic Pain After Dental Implant Surgery: Literature Review and Proposed Algorithm for Medicosurgical Treatment.

The objective of this study is to establish an algorithm for the medicosurgical treatment of dental implant-induced neuropathic pain. The methodology was based on the good practice guidelines from the French National Authority for Health: the data were searched on the Medline database. A working group has drawn up a first draft of professional recommendations corresponding to a set of qualitative summaries. Consecutive drafts were amended by the members of an interdisciplinary reading committee. A total of 91 publications were screened, of which 26 were selected to establish the recommendations: 1 randomized clinical trial, 3 controlled cohort studies, 13 case series, and 9 case reports. In the event of the occurrence of post-implant neuropathic pain, a thorough radiological assessment by at least a panoramic radiograph (orthopantomogram) or especially a cone-beam computerized tomography scan is recommended to ensure that the tip of the implant is placed more than 4 mm from the anterior loop of the mental nerve for an anterior implant and 2 mm from the inferior alveolar nerve for a posterior implant. Very early administration of high-dose steroids, possibly associated with partial unscrewing or full removal of the implant preferably within the first 36-48 hours after placement, is recommended. A combined pharmacological therapy (anticonvulsants, antidepressants) could minimize the risk of pain chronicization. If a nerve lesion occurs in the context of dental implant surgery, treatment should be initiated within the first 36-48 hours after implant placement, including partial or full removal of the implant and early pharmacological treatment.

Metasurface-enhanced light detection and ranging technology.

Deploying advanced imaging solutions to robotic and autonomous systems by mimicking human vision requires simultaneous acquisition of multiple fields of views, named the peripheral and fovea regions. Among 3D computer vision techniques, LiDAR is currently considered at the industrial level for robotic vision. Notwithstanding the efforts on LiDAR integration and optimization, commercially available devices have slow frame rate and low resolution, notably limited by the performance of mechanical or solid-state deflection systems. Metasurfaces are versatile optical components that can distribute the optical power in desired regions of space. Here, we report on an advanced LiDAR technology that leverages from ultrafast low FoV deflectors cascaded with large area metasurfaces to achieve large FoV (150°) and high framerate (kHz) which can provide simultaneous peripheral and central imaging zones. The use of our disruptive LiDAR technology with advanced learning algorithms offers perspectives to improve perception and decision-making process of ADAS and robotic systems.

Separating arbitrary free-space beams with an integrated photonic processor.

Free-space optics naturally offers multiple-channel communications and sensing exploitable in many applications. The different optical beams will, however, generally be overlapping at the receiver, and, especially with atmospheric turbulence or other scattering or aberrations, the arriving beam shapes may not even be known in advance. We show that such beams can be still separated in the optical domain, and simultaneously detected with negligible cross-talk, even if they share the same wavelength and polarization, and even with unknown arriving beam shapes. The kernel of the adaptive multibeam receiver presented in this work is a programmable integrated photonic processor that is coupled to free-space beams through a two-dimensional array of optical antennas. We demonstrate separation of beam pairs arriving from different directions, with overlapping spatial modes in the same direction, and even with mixing between the beams deliberately added in the path. With the circuit's optical bandwidth of more than 40 nm, this approach offers an enabling technology for the evolution of FSO from single-beam to multibeam space-division multiplexed systems in a perturbed environment, which has been a game-changing transition in fiber-optic systems.

Amorphous-silicon visible-light detector integrated on silicon nitride waveguides.

Visible-light integrated photonics is emerging as a promising technology for the realization of optical devices for applications in sensing, quantum information and communications, imaging, and displays. Among the existing photonic platforms, high-index-contrast silicon nitride (Si3N4) waveguides offer broadband transparency in the visible spectral range and a high scale of integration. As the complexity of photonic integrated circuits (PICs) increases, on-chip detectors are required to monitor their working point for reconfiguration and stabilization operations. In this Letter, we present a semi-transparent in-line power monitor integrated on Si3N4 waveguides that operates in the red-light wavelength range (660 nm). The proposed device exploits the photoconductivity of a hydrogenated amorphous-silicon (a-Si:H) film that is evanescently coupled to an optical waveguide. Experimental results show a responsivity of 30 mA/W, a sensitivity of -45 dBm, and a sub-µs time response. These features enable the use of the proposed photoconductor for high-sensitivity monitoring and control of visible-light Si3N4 PICs.

Ketamine in chronic pain: A Delphi survey.

BACKGROUND: There is no recommendation in Europe for the use of ketamine in patients with chronic pain. The heterogeneity of practice highlights the need to seek the advice of experts in order to establish a national consensus. This Delphi survey aimed to reach a national consensus on the use of ketamine in chronic pain in Pain clinics. METHODS: A collaborative four-round internet-based questionnaire was used. It was created after literature search on ketamine administration in chronic pain and included about 96 items. It discussed utility and advantages, adverse events and deleterious aspects, methods of administration, concomitant treatments and assessment of results. RESULTS: Twenty-eight experts completed all rounds of the survey with a total of 81.3% items reaching a consensual answer. Neuropathic pain represents the first indication to use ketamine, followed, with a good to moderate utility, by other situations (fibromyalgia, complex regional pain syndrome, central neuropathic pain, peripheral neuropathic pain, nociceptive pain, sensitization, opioid withdrawal, palliative care, depression). Experts agreed on the rare occurrence of adverse events. Concerning routes of administration, intravenous infusion with doses of 0.5-0.9 mg/kg/d for 4 days of treatment is preferred. Place of care is hospital, as in- or out-patient, with a quarterly administration of ketamine. Finally, ketamine effectiveness is assessed 1 month after infusion, and experts encourage combination with non-pharmacological treatment. CONCLUSIONS: This Delphi survey established a consensus of pain specialists on the use of ketamine in refractory chronic pain, thus providing a basis for future comparative trials. SIGNIFICANCE: This Delphi survey in chronic pain reached agreement on four main aspects: (1) Priority to treat neuropathic pain with evaluation of effectiveness at 1 month; (2) No deleterious effects in the majority of listed diseases/situations with the absence or <3% of suggested adverse events; (3) 0.5-0.9 mg/kg/d IV infusion; (4) Combination with non-pharmacological treatment.

High precision integrated photonic thermometry enabled by a transfer printed diamond resonator on GaN waveguide chip.

We demonstrate a dual-material integrated photonic thermometer, fabricated by high accuracy micro-transfer printing. A freestanding diamond micro-disk resonator is printed in close proximity to a gallium nitride on a sapphire racetrack resonator, and respective loaded Q factors of 9.1 × 104 and 2.9 × 104 are measured. We show that by using two independent wide-bandgap materials, tracking the thermally induced shifts in multiple resonances, and using optimized curve fitting tools the measurement error can be reduced to 9.2 mK. Finally, for the GaN, in a continuous acquisition measurement we record an improvement in minimum Allan variance, occurring at an averaging time four times greater than a comparative silicon device, indicating better performance over longer time scales.

Differences in stabilometric correlates of pain relief after wearing postural insoles for six weeks between chronic nociceptive and neuropathic foot pain. An open-label pilot study.

OBJECTIVE: The aim of this study was to determine if the use of postural insoles could result in a noticeable reduction in the foot pain intensity in patients with a chronic pain condition, either nociceptive (ankylosing spondylitis, AS) or neuropathic (small fiber neuropathy, SFN). METHOD: In this open-label pilot study, patients were asked to wear postural insoles for a continuous period of 6 weeks. The primary endpoint was the mean daily pain intensity at foot mobilization measured using a visual analogue scale (VAS). The secondary endpoints included global pain intensity scores (at rest or under mobilization), clinical questionnaires on pain and daily functioning (including the Brief Pain Inventory (BPI), the Bath Ankylosing Spondylitis Disease Activity Index (BASDAI), the Neuropathic Pain Symptom Inventory (NPSI) and the DN4 questionnaire), and posturo-podiatric variables assessed on clinical examination or using a baro-stabilometric platform. RESULTS: The study was completed by 17 patients with AS and 12 patients with SFN. After wearing postural insoles for 6 weeks, a significant improvement was observed on the primary endpoint (decrease in VAS pain score at the foot during mobilization) in both groups of patients (from 6.4 ±â€¯2.4 to 3.6 ±â€¯2.6 (p = 0.0004) in the AS group and from 5.7 ±â€¯2.2 to 2.4 ±â€¯1.6 (p = 0.0003) in the SFN group). Improvement was also observed for all other pain and activity scores (global pain at rest or during mobilization (VAS), BDI, and BASDAI for the AS group or NPSI and DN4 for the SFN group), as well as for posturo-podiatric clinical variables. However, we did not find any difference in any clinical pain score whether the posturo-podiatric clinical outcomes were positive or not. Regarding the stabilometric measures, the only significant change after the intervention was a reduced mean velocity of center of pressure displacement in the AS group only (mVel in mm/s: from 7.4 ±â€¯2.0 vs. 6.7 ±â€¯1.9, p = 0.017). In addition, the reduction in mVel correlated to that of the BPI score (r = 0.48, p = 0.0496). CONCLUSION: In both groups of patients, wearing postural insoles for 6 weeks led to a significant decrease in local pain intensity at foot level and to more global analgesic effects and positive posturo-podiatric changes. However, these latter changes did not appear to be strongly associated with pain relief. Nevertheless, an index of a better postural control, i.e. mVel decrease, was found to be related to a reduction of pain interference in daily life activities in AS patients, but not in SFN patients. Therefore, in the context of neuropathic pain, mechanisms other than postural changes likely contribute to the analgesic effects of wearing postural insoles, in contrast to nociceptive pain due to spinal osteoarthritis.

AlGaAs-on-insulator waveguide for highly efficient photon-pair generation via spontaneous four-wave mixing.

We report on the generation of correlated photon pairs in AlGaAs-on-insulator (AlGaAs-OI) waveguides through nonlinear spontaneous four-wave-mixing (SFWM). Our measurements reveal an SFWM pair generation efficiency of ∼0.096×1012pairs/(sW2) at a wavelength of 1550 nm. This is one of the highest efficiencies achieved to date for integrated SFWM sources. A maximal coincidence-to-accidental ratio of ∼122 is measured. A spectral characterization of the device's pair emission at the quantum level demonstrates a broad generation bandwidth of 2.0 THz, which is important for frequency multiplexing applications. Our results indicate that AlGaAs-OI is an efficient material platform for integrated quantum photonics at telecom wavelengths.

Supercontinuum generation in dispersion engineered AlGaAs-on-insulator waveguides.

The effect of engineering the dispersion of AlGaAs-on-insulator (AlGaAs-OI) waveguides on supercontinuum generation is investigated at telecom wavelengths. The pronounced effect the waveguide width has on the nonlinear dynamics governing the supercontinua is systematically analyzed and the coherence of the spectra verified with numerical simulations. Using dispersion engineered AlGaAs-OI waveguides, broadband supercontinua were readily obtained for pulse energies of [Formula: see text] and a device length of only 3 mm. The results presented here, further understanding of the design and fabrication of this novel platform and describe the soliton and dispersive wave dynamics responsible for supercontinuum generation. This study showcases the potential of AlGaAs-OI for exploring fundamental physics and realizing highly efficient, compact, nonlinear devices.

Automated Nanoscale Absolute Accuracy Alignment System for Transfer Printing.

The heterogeneous integration of micro- and nanoscale devices with on-chip circuits and waveguide platforms is a key enabling technology, with wide-ranging applications in areas including telecommunications, quantum information processing, and sensing. Pick and place integration with absolute positional accuracy at the nanoscale has been previously demonstrated for single proof-of-principle devices. However, to enable scaling of this technology for realization of multielement systems or high throughput manufacturing, the integration process must be compatible with automation while retaining nanoscale accuracy. In this work, an automated transfer printing process is realized by using a simple optical microscope, computer vision, and high accuracy translational stage system. Automatic alignment using a cross-correlation image processing method demonstrates absolute positional accuracy of transfer with an average offset of <40 nm (3σ < 390 nm) for serial device integration of both thin film silicon membranes and single nanowire devices. Parallel transfer of devices across a 2 × 2 mm2 area is demonstrated with an average offset of <30 nm (3σ < 705 nm). Rotational accuracy better than 45 mrad is achieved for all device variants. Devices can be selected and placed with high accuracy on a target substrate, both from lithographically defined positions on their native substrate or from a randomly distributed population. These demonstrations pave the way for future scalable manufacturing of heterogeneously integrated chip systems.

Thermo-optic coefficient of PECVD silicon-rich silicon nitride.

The thermo-optic coefficient (TOC) of photonic integrated waveguides fabricated on silicon-rich silicon nitride grown by plasma-enanched chemical vapor deposition is characterized for the first time, to the best of our knowledge. The TOC is found to increase linearly with the fractional composition of silicon over a range from that of silicon nitride to a-Si. This finding is significant for improving the power efficiency of thermally tuned photonic integrated circuits.

Trimming of silicon-on-insulator ring-resonators via localized laser annealing.

We propose a post-fabrication trimming method for the silicon-on-insulator photonic platform based on localised laser annealing of hydrogen silsesquioxane (HSQ) cladding. The technique is fast, does not degrade the device performance, does not require additional fabrication steps, and can therefore be implemented at minimal cost. Here we experimentally demonstrated how the spectrum of a ring resonator can be shifted by over 1 nm by annealing a section of the device as short as 30 µm, corresponding to a change in the effective refractive index of ∼10-2. Modifications of both the HSQ refractive index and its chemical structure as a function of the annealing temperature are also discussed. Trimming of multi-ring resonators indicate that this technique can be effectively used for post-fabrication reconfiguration of complex photonic circuits or to compensate for the fabrication tolerances of a typical CMOS process.

Picosecond ultrasonics with miniaturized semiconductor lasers.

There is a great desire to extend ultrasonic techniques to the imaging and characterization of nanoobjects. This can be achieved by picosecond ultrasonics, where by using ultrafast lasers it is possible to generate and detect acoustic waves with frequencies up to terahertz and wavelengths down to nanometers. In our work we present a picosecond ultrasonics setup based on miniaturized mode-locked semiconductor lasers, whose performance allows us to obtain the necessary power, pulse duration and repetition rate. Using such a laser, we measure the ultrasonic echo signal with picosecond resolution in a 112 nm thick Al film deposited on a semiconductor substrate. We show that the obtained signal is as good as the signal obtained with a standard bulky mode-locked Ti-Sa laser. The experiments pave the way for designing integrated portable picosecond ultrasonic setups on the basis of miniaturized semiconductor lasers.