All-solid-state VUV frequency comb at 160 nm using high-harmonic generation in nonlinear femtosecond enhancement cavity

© 2019 Optical Society of America. Users may use, reuse, and build upon the article, or use the article for text or data mining, so long as such uses are for non-commercial purposes and appropriate attribution is maintained. All other rights are reserved.We realized a solid-state-based vacuum ultraviolet frequency comb by harmonics generation in an external enhancement cavity. Optical conversions were so far reported by only using gaseous media. We present a theory that allows the most suited solid generation medium to be selected for specific target harmonics by adapting the material’s bandgap. We experimentally use a thin AlN film grown on a sapphire substrate to realize a compact frequency comb high-harmonic source in the Deep Ultraviolet (DUV)/Vacuum Ultraviolet/Deep Ultraviolet (VUV) spectral range. By extending our earlier VUV source [Opt. Express 26, 21900 (2018)] with the enhancement cavity, a sub-Watt level Ti:sapphire femtosecond frequency comb is enhanced to 24 W stored average power, its 3rd, 5th, and 7th harmonics are generated, and the targeted 5th harmonic’s power at 160 nm increased by two orders of magnitude. The emerging nonlinear effects in the solid medium, together with suitable intra-cavity dispersion management, support optimal enhancement and stable locking. To demonstrate the realized frequency comb’s spectroscopic ability, we report on the beat measurement between the 3rd harmonic beam and a 266 nm CW laser reaching about 1 MHz accuracy.Peer ReviewedPostprint (published version

Diode laser modules based on laser-machined, multi-layer ceramic substrates with integrated water cooling and micro-optics

This thesis presents a study on the use of low temperature co-fired ceramic (LTCC) material as a new platform for the packaging of multiple broad area single emitter diode lasers. This will address the recent trend in the laser industry of combining multiple laser diodes in a common package to reach the beam brightness and power required for pumping fibre lasers and for direct-diode industrial applications, such as welding, cutting, and etching. Packages based on multiple single emitters offer advantages over those derived from monolithic diode bars such as higher brightness, negligible thermal crosstalk between neighbouring emitters and protection against cascading failed emitters. In addition, insulated sub-mounted laser diodes based on telecommunication standards are preferred to diode bars and stacks because of the degree of assembly automation, and improved lifetime. At present, lasers are packaged on Cu or CuW platforms, whose high thermal conductivities allow an efficient passive cooling. However, as the number of emitters per package increases and improvements in the laser technology enable higher output power, the passive cooling will become insufficient. To overcome this problem, a LTCC platform capable of actively removing the heat generated by the lasers through impingement jet cooling was developed. It was provided with an internal water manifold capable to impinge water at 0.15 lmin-1 flow rate on the back surface of each laser with a variation of less than 2 °C in the temperature between the diodes. The thermal impedance of 2.7°C/W obtained allows the LTCC structure to cool the latest commercial broad area single emitter diode lasers which deliver up to 13 W of optical power. Commonly, the emitters are placed in a “staircase” formation to stack the emitters in the fast-axis, maintaining the brightness of the diode lasers. However, due to technical difficulties of machining the LTCC structure with a staircase-shaped face, a novel out-plane beam shaping method was proposed to obtain an elegant and compact free space combination of the laser beam on board using inexpensive optics. A compact arrangement was obtained using aligned folding mirrors, which stacked the beams on top of each other in the fast direction with the minimum dead space

Aluminum nitride deposition/characterization & pMEMs/SAW device simulation/fabrication

Aluminum Nitride (AlN) is a promising material for piezoelectric MicroElectroMechanical Systems (pMEMS) and Surface Acoustic Wave (SAW) devices. AlN is a direct bandgap semiconductor possessing moderate piezoelectric coefficients, a high Curie temperature, and a high acoustic velocity. Potential applications of AlN thin film devices include high temperature pMEMS microvalves for use in Solid Oxide Fuel Cell (SOFC) flow control systems and high frequency/sensitivity SAW platforms for use in biosensors.;Since AlN is a robust material capable of operating at high temperatures and harsh environments, it can be used in settings where other widely used piezoelectrics such as Lead Zirconate Titanate (PZT) and Zinc Oxide (ZnO) fail. Piezoelectric beams are commonly used in MEMS and have many possible applications in smart sensor and actuator systems. In this work, the results of 3-dimensional Finite Element Analysis (FEA) of AlN homogeneous bimorphs (d31 mode) are shown. The coupled-field FEA simulations were performed using the commercially available software tool ANSYSRTM Academic Research, v.11.0. The effect of altering the contact geometry and position on the displacement, electric field, stress, and strain distributions for the static case is reported.;Surface acoustic wave devices have drawn increasing interest for use as highly sensitive sensors. Specifically, SAW platforms are being explored for chemical and biological sensor applications. Because AlN has one of the highest acoustic velocities of all the piezoelectric materials, high frequency (and thus highly sensitive) sensors are feasible. In this work, AlN SAW Rayleigh wave platforms were designed, fabricated, and tested. The insertion loss of the SAW platforms for two InterDigitated Transducers (IDTs) separation distances is also presented

Integrated sensors for process monitoring and health monitoring in microsystems

This thesis presents the development of integrated sensors for health monitoring in Microsystems, which is an emerging method for early diagnostics of status or “health” of electronic systems and devices under operation based on embedded tests. Thin film meander temperature sensors have been designed with a minimum footprint of 240 m × 250 m. A microsensor array has been used successfully for accurate temperature monitoring of laser assisted polymer bonding for MEMS packaging. Using a frame-shaped beam, the temperature at centre of bottom substrate was obtained to be ~50 ºC lower than that obtained using a top-hat beam. This is highly beneficial for packaging of temperature sensitive MEMS devices. Polymer based surface acoustic wave humidity sensors were designed and successfully fabricated on 128° cut lithium niobate substrates. Based on reflection signals, a sensitivity of 0.26 dB/RH% was achieved between 8.6 %RH and 90.6 %RH. Fabricated piezoresistive pressure sensors have also been hybrid integrated and electrically contacted using a wire bonding method. Integrated sensors based on both LiNbO3 and ZnO/Si substrates are proposed. Integrated sensors were successfully fabricated on a LiNbO3 substrate with a footprint of 13 mm × 12 mm, having multi monitoring functions for simultaneous temperature, measurement of humidity and pressure in the health monitoring applications

Microfabrication of heated nebulizer chips for mass spectrometry

Microfabrication technologies originating from the semiconductor industry were applied to the instrumentation of analytical chemistry. Heated nebulizer (HN) chips made of silicon and glass were developed. The HN chips are used to vaporize a sample prior to detection by a mass spectrometer. The chips can be used with both liquid and gaseous samples and they are compatible with multiple atmospheric pressure ionization techniques, which enables wide applicability with different separation methods and various types of analytes. Better sensitivity, flexibility and operation with a lower sample and nebulizer gas flow rates was achieved by the miniaturization of the heated nebulizer. The chips can operate with 50 nL min-1 to 5 µL min-1 sample flow rates typical of microfluidic separation systems. Silicon and glass microfabrication methods - etching, wafer bonding and thin film technology - were developed and applied to the fabrication of the HN chips in 40 different layout and process variations. The thermal behaviour of the chips and the shape of the gaseous jet produced by the chips was studied. A method was developed for measuring the temperature distribution of a gaseous jet using a miniature thermocouple attached to a computer controlled xyz stage. Different methods for making capillary tube and electrical interconnections to the chips were also studied. Liquid chromatography (LC) column chips were developed resulting in an integrated chip having both an LC column and a heated nebulizer on a single chip. At the end of the LC column there is a high aspect ratio micropillar frit which enables packing the column with particles. The novel chips developed in this work extend the available ionization methods and the range of suitable analytes compared to the previously presented chips for mass spectrometry

Microfabrication of heated nebulizer chips for mass spectrometry

Microfabrication technologies originating from the semiconductor industry were applied to the instrumentation of analytical chemistry. Heated nebulizer (HN) chips made of silicon and glass were developed. The HN chips are used to vaporize a sample prior to detection by a mass spectrometer. The chips can be used with both liquid and gaseous samples and they are compatible with multiple atmospheric pressure ionization techniques, which enables wide applicability with different separation methods and various types of analytes. Better sensitivity, flexibility and operation with a lower sample and nebulizer gas flow rates was achieved by the miniaturization of the heated nebulizer. The chips can operate with 50 nL min-1 to 5 µL min-1 sample flow rates typical of microfluidic separation systems. Silicon and glass microfabrication methods - etching, wafer bonding and thin film technology - were developed and applied to the fabrication of the HN chips in 40 different layout and process variations. The thermal behaviour of the chips and the shape of the gaseous jet produced by the chips was studied. A method was developed for measuring the temperature distribution of a gaseous jet using a miniature thermocouple attached to a computer controlled xyz stage. Different methods for making capillary tube and electrical interconnections to the chips were also studied. Liquid chromatography (LC) column chips were developed resulting in an integrated chip having both an LC column and a heated nebulizer on a single chip. At the end of the LC column there is a high aspect ratio micropillar frit which enables packing the column with particles. The novel chips developed in this work extend the available ionization methods and the range of suitable analytes compared to the previously presented chips for mass spectrometry

Study, automation and planning of micromachining processes based on infrared pulsed Fiber Laser

Short-pulsed Fiber Lasers represent an ideal solution for many micromachining operations due to their high quality laser beam and strong focusability. In this thesis, micromachining processes based on infrared pulsed Fiber Laser were investigated. A laser micromachining setup based on a 10 W Yb-doped pulsed Fiber laser source was designed, integrated and automated in order to conduct experimental activity. A new approach to part programming for laser micromachining based on syntax-free, non-structured natural language text was proposed. Experimental work was conducted by means of the pulsed Fiber Laser micromachining setup on metal and non-metal surfaces. The experiments proved that Fiber Lasers are well suited to the micromachining tasks