Design of a metal-based deformable mirror for orthogonal beam deflection and highly dynamic beam oscillation.

We report on an opto-mechanical metal mirror design for highly dynamic, diffraction-limited focus shifting. Here, the mechanical geometry of the membrane is of crucial interest as it must provide sufficient optical performance to allow for diffraction limited focussing and have a high mechanical eigenfrequency to provide dynamic motions. The approach is the analytical consideration of the plate theory and provides the basis for a parameterized finite element model. By means of an finite element analysis (FEA), essential steps for the optimization of the mirror design with respect to a wide range of optical power and a high operating frequency are shown. To verify the results of the FE analysis, the deformed surface is decomposed into Zernike coefficients. An analysis of the point spread function is performed to evaluate the optical performance. For dynamic evaluation a modal and a harmonic vibration analysis are conducted. The opto-mechanical design allows a biconical deformation of the mirror surface, enabling the generation of a diffraction-limited spot diameter in the adjustment range of ±1.2 dpt. The surface shape error in this range is 53 nm. The dynamic analysis shows the first excited eigenfrequency at 21.6 kHz and a diffraction-limited operation frequency at 9.5 kHz. This paper provides an alternative design approach for highly dynamic beam oscillation in the Z direction, forming a complement to highly dynamic X-Y scanning systems.

Design routine and characterisation of a biconic deformable metal mirror for focus shifting.

This paper describes an opto-mechanical concept of a deformable metal mirror membrane, which can shift the focus position over a large range by use of a single actuator. The core element of the mirror is a diamond turned tulip-shaped membrane, the design is optimized to correct astigmatic aberrations which arise from the use of a curved mirror under a deflection angle. For this purpose, the target mirror surface is biconic. The manufactured mirror was tested with a maximum central deflection of 28 µm and, when used in combination with a 200 mm focal lens, is capable of producing a focus shift of up to 17.9 mm with a resulting wavefront aberration of 238.7 nm RMSerror.

Validation of pre-compensation under point-ahead-angle in a 1 km free-space propagation experiment.

Adaptive optical pre-compensation is seen as crucial for free-space laser communication in order to overcome the influence of atmospheric turbulence, particularly with respect to Earth-to-GEO feederlinks. This paper presents an experimental investigation into adaptive optical pre-compensation under large point-ahead-angles. We detail the design and realization of a free-space laser communication experiment over a 1.0 km horizontal path using a divergent beacon beam and a focussed signal beam, propagating in opposite directions. We describe the design and development of our experimental setup and measurement campaign using real turbulence. The median isoplanatic angle was calculated to be 0.16 mrad, while an increase in the received optical power through pre-compensation could be demonstrated for point-ahead-angles in the range of 0.13 mrad to 0.27 mrad.

Using Lean Six Sigma to improve rates of day of surgery admission in a national thoracic surgery department.

OBJECTIVE: The aim of this study is to improve rates of day of surgery admission (DOSA) for all suitable elective thoracic surgery patients. DESIGN: Lean Six Sigma (LSS) methods were used to enable improvements to both the operational process and the organizational working of the department over a period of 19 months. SETTING: A national thoracic surgery department in a large teaching hospital in Ireland. PARTICIPANTS: Thoracic surgery staff, patients and quality improvement staff at the hospital. INTERVENTION(S): LSS methods were employed to identify and remove the non-value-add in the patient's journey and achieve higher levels of DOSA. A pre-surgery checklist and Thoracic Planning Meeting were introduced to support a multidisciplinary approach to enhanced recovery after surgery (ERAS), reduce rework, improve list efficiency and optimize bed management. MAIN OUTCOME MEASURE(S): To achieve DOSA for all suitable elective thoracic surgery patients in line with the National Key Performance Indicator of 75%. A secondary outcome would be to further decrease overall length of stay by 1 day. RESULTS: Over a 19 month period, DOSA has increased from 10 to 75%. Duplication of preoperative tests reduced from 83 to <2%. Staff and patient surveys show increased satisfaction and improved understanding of ERAS. CONCLUSIONS: Using LSS methods to improve both operational process efficiency and organizational clinical processes led to the successful achievement of increasing rates of DOSA in line with national targets.

Experimental validation of phase-only pre-compensation over 494 m free-space propagation.

It is anticipated that ground-to-geostationary orbit (GEO) laser communication will benefit from pre-compensation of atmospheric turbulence for laser beam propagation through the atmosphere. Theoretical simulations and laboratory experiments have determined its feasibility; extensive free-space experimental validation has, however, yet to be fulfilled. Therefore, we designed and implemented an adaptive optical (AO)-box which pre-compensates an outgoing laser beam (uplink) using the measurements of an incoming beam (downlink). The setup was designed to approximate the baseline scenario over a horizontal test range of 0.5 km and consisted of a ground terminal with the AO-box and a simplified approximation of a satellite terminal. Our results confirmed that we could focus the uplink beam on the satellite terminal using AO under a point-ahead angle of 28 µrad. Furthermore, we demonstrated a considerable increase in the intensity received at the satellite. These results are further testimony to AO pre-compensation being a viable technique to enhance Earth-to-GEO optical communication.

Temporally-stable active precision mount for large optics.

We present a temporally-stable active mount to compensate for manufacturing-induced deformations of reflective optical components. In this paper, we introduce the design of the active mount, and its evaluation results for two sample mirrors: a quarter mirror of 115 × 105 × 9 mm3, and a full mirror of 228 × 210 × 9 mm3. The quarter mirror with 20 actuators shows a best wavefront error rms of 10 nm. Its installation position depending deformations are addressed by long-time measurements over 14 weeks indicating no significance of the orientation. Size-induced differences of the mount are studied by a full mirror with 80 manual actuators arranged in the same actuator pattern as the quarter mirror. This sample shows a wavefront error rms of (27±2) nm over a measurement period of 46 days. We conclude that the developed mount is suitable to compensate for manufacturing-induced deformations of large reflective optics, and likely to be included in the overall systems alignment procedure.

An exploratory study of psychosis risk factors in individuals who are referred but do not meet criteria for an early intervention in psychosis service.

BACKGROUND: The 'at-risk mental state' (ARMS) for psychosis has been critiqued for its limited prognostic ability and identification of a limited proportion of those who will develop a first episode of psychosis (FEP). Broadening the search for high-risk groups is key to improving population-level ascertainment of psychosis risk. AIMS: To explore risk enrichment in diagnostic, demographic and socio-functional domains among individuals referred to an early intervention in psychosis (EIP) service not meeting ARMS or FEP criteria. METHOD: A retrospective file review of 16 years of referrals to a tertiary EIP service in Ireland was undertaken. Diagnostic outcomes from standardised assessments (Structured Clinical Interview for DSM), demographic (age, gender, family history, nationality) and socio-occupational (relationship status, living status, working status) variables were compiled for those not meeting criteria. These were compared with individuals diagnosed with an FEP in the same period. RESULTS: From 2005 to 2021 inclusive, of 2025 index assessments, 27.6% (n = 558) did not meet either FEP or ARMS criteria, which is notably higher than the 5.4% (n = 110) meeting ARMS criteria. This group had high psychiatric morbidity, with 65.4% meeting criteria for at least one DSM Axis I disorder. Depressive, anxiety and substance use disorders predominated. Their functional markers were poor, and comparable to the FEP cohort. CONCLUSIONS: This group is enriched for psychosis risk factors. They are a larger group than those meeting ARMS criteria, a finding that may reflect EIP service configuration. They may be an important focus for further study in the search for at-risk populations beyond the current ARMS model.

Critical COVID-19 in a pregnant patient who presented in starvation ketoacidosis with a background history of acrorenal syndrome.

A primiparous woman in her late 30s at 28+1 weeks' gestation presented with a 3-day history of abdominal pain, loss of appetite, nausea and vomiting and was diagnosed with starvation ketoacidosis. A routine admission swab returned positive for COVID-19. She had been diagnosed with acrorenal syndrome from birth. Three days post admission, she deteriorated rapidly into respiratory failure requiring intubation and ventilation. She was treated with dexamethasone, prophylactic enoxaparin, a course of piperacillin/tazobactam followed by meropenem and fluconazole and 8 cycles of proning. An emergency caesarean section was performed on day 12 of hospital admission at 29+5 weeks' gestation to improve maternal oxygenation and ventilation. The baby had deformities consistent with acrorenal syndrome but no evidence of COVID-19. She spent 23 days in the intensive care unit. Our case describes an unusual presentation of COVID-19, the challenges in managing critically ill pregnant patients along with a rare background history of acrorenal syndrome.