Heterogeneously integrated microdisk lasers for optical interconnects and optical logic

Optical interconnect and optical packet switching systems could take advantage of small footprint, low power lasers and optical logic elements. Microdisk lasers, with a diameter below 10 mu m and fabricated in InP membranes with a high index contrast, offer this possibility at the telecom wavelengths. The lasers are fabricated using heterogeneous integration of InP membranes on silicon-on-insulator (SOI) passive waveguide circuits, which allows to combine the active elements with compact, high-index contrast passive elements. The lasing mode in such microdisk lasers is a whispering gallery mode, which can be either in the clockwise (CW) or counter clockwise direction (CCW) or in both. The coupling to the SOI wire waveguides is through evanescent coupling. Predefined, unidirectional operation can be achieved by terminating the SOI wires at one end with Bragg gratings. For all-optical flip-flops, the laser operation must be switchable between CW and CCW, using short optical pulses. Unidirectional operation in either direction is only possible if the coupling between CW and CCW direction is very small, requiring small sidewall surface roughness, and if the gain suppression is sufficiently large, requiring large internal power levels. All-optical flip-flops based on microdisk lasers with diameter of 7.5 mu m have been demonstrated. They operate with a CW power consumption of a few mW and switch in 60ps with switching energies as low as 1.8fJ. Operation as all-optical gate has also been demonstrated. The surface roughness is limited through optimized etching of the disks and the large internal power is obtained through good heat sink

Enhanced Balmer-[MATH] emission in interpenetrating plasmas

The interpenetration of laser produced plasmas can be detected by the occurrence of charge exchange reactions. Such reactions only occur if highly charged ions collide with ions of a significantly lower charge in suitable energy levels. This leads to selective population of a specific level of the highly charged ion resulting in an enhancement of particular lines in the region of the interaction. In case of interpenetrating carbon plasmas these reactions lead to enhanced line emission at 18.2 nm (H[MATH] line of C VI). We present spatially and temporally resolved investigations of the interaction region of colliding plasmas ; we show results of calculations of the cross sections for charge exchange obtained with a semi-classical model and compare measured spectra with calculated ones obtained from a collisional radiative model

Monolithic optical components for splitting of high-power beams

Highly efficient beam splitters are important for a variety of high power laser applications. We prove different approaches like aperture and amplitude splitting for practicability for single- and multimode laser sources. Combining of micro- and macro-optical fabrication technologies allows novel monolithic free form splitting components with implemented segmented or stepless diffractive optical surfaces. The monolithic components are robust, compact and low weight and easy in handling. Here, we present two monolithic components: a segmented free form 1-to-17 beam splitter for fibre coupled lasers and a diffractive 1-to-11 beam splitter for single mode lasers with peak-to-peak pitch of 1.25mm and 0.8mm, respectively. The optical designs, the manufacturing of the prototypes as well as surface and performance measurements are reported. The prototypes from Fused Silica and Calcium Fluoride are designed for 532nm and 1064nm wavelength. Simulations show efficiencies larger than 98% and peak-to-peak non-uniformity below±3.2%. First laboratory results confirm efficiencies of < 95% and peak-to-peak non-uniformity of less than ±5%

High throughput EUV-reflectometer for EUV mask-blanks

A prototype of a reflectometer for masks and mask blanks has been set-up in autumn 2003 for in-house quality check of EUV mask blanks at Schott Lithotec. The target specifications are those under discussion as SEMI standard for EUV mask blank reflectometry. Additionally, the identified demands for semiconductor capital investment for future actinic EUV metrology, high throughputs and small measuring spots, were taken into account for the tool development. Effective use of the emission from a laboratory discharge source is achieved by using polychromatic reflectometry, which has been shown to deliver results about a factor of 100 faster with the same source power and needs less mechanical overhead than a monochromatic reflectometer. The hardware concept, first results and discussion of a test of the performance with respect to resolution, uncertainty and reproducibility will be represented. Jointly with the Physikalisch-Technische Bundesanstalt's laboratory for radiometr y at BESSY II the traceability to storage ring metrology, the calibration and the validation of the concepts will be assessed

High-performance 6-inch EUV mask blanks produced under real production conditions by ion-beam sputter deposition

EUV mask blanks consist of two thin film systems deposited on low thermal expansion 6 inch substrates (LTEM). First there is the multilayer stack with around 100 alternating layers of elements with different optical properties which are topped by a capping layer. The absorber stack which consists of a buffer and a absorber layer is next. Here a minimum absorption of EUV light of 99 % is required. The stress in both layer systems should be as low as possible. The reduction of defects to an absolute minimum is one of the main challenges. The high-reflective Mo/Si multilayer coatings were designed for normal incidence reflectivity and successfully deposited on 6-inch LTEM substrates by ion-beam sputtering. X-ray scattering, transmission electron microscopy and atomic force microscopy were used for characterization of the multilayer interfaces and the surface morphology. The results are correlated to the measured normal incidence reflectivity using synchrotron radiation at the "Physikalisch- Technischen Bundesanstalt" (PTB) reflectometer at BESSY II, Berlin, Germany. A high resolution laser scanner was used to measure the particle distribution. First multilayer defect results are presented

Preliminary results from key experiments on sources for EUV lithography

While huge progress has been achieved for EUVL system design and multilayer optics during the last years the decision on the best suited source is still open. In a German basic research cooperation on short-wavelength plasma based sources some key issues also relevant for EUVL are addressed: the comparison of existing sources, investigations on the scalability of source concepts and the demonstration of key features. Preliminary results of investigations on parameters for best conversion efficiency of laser produced plasmas, concepts for high-power lasers and scalability of gas discharge based sources are presented. Comparability of results is assured by calibrated metrology tools which are cross checked with ASML’s flying circus