A Smart Procedure for the Femtosecond Laser-Based Fabrication of a Polymeric Lab-on-a-Chip for Capturing Tumor Cell

Rapid prototyping methods for the design and fabrication of polymeric labs-on-a-chip are on the rise,as they allow high degrees of precision and flexibility.For example,a microfluidic platform may require an optimization phase in which it could be necessary to continuously modify the architecture and geometry;however,this is only possible if easy,controllable fabrication methods and low-cost materials are available.In this paper,we describe the realization process of a microfluidic tool,from the computer-aided design(CAD)to the proof-of-concept application as a capture device for circulating tumor cells(CTCs).The entire platform was realized in polymethyl methacrylate(PMMA),combining femtosecond(fs)laser and micromilling fabrication technologies.The multilayer device was assembled through a facile and low-cost solvent-assisted method.A serpentine microchannel was then directly biofunctionalized by immobilizing capture probes able to distinguish cancer from non-cancer cells without labeling.The low material costs,customizable methods,and biological application of the realized platform make it a suitable model for industrial exploitation and applications at the point of care.

Whitlockite has a characteristic distribution in mammary microcalcifications and it is not associated with breast cancer

Dear Editor,Microcalcifications(MCs)are common findings in mammography and can be indicative of different degrees of malignancy,thus requiring multiple stereotaxis vacuumassisted biopsies under mammography to identify and characterize breast cancer[1,2].In many cases,however,the presence of MCs is not associated with the presence of a tumor.Therefore,a better understanding of the physical-chemical properties of MCs is needed to assess the relationship between their presence and breast cancer.

Spatial Aberrations in High-Order Harmonic Generation

We investigate the spatial characteristics of high-order harmonic radiation generated in argon and observe cross-like patterns in the far field.An analytical model describing harmonics from an astigmatic driving beam reveals that these patterns result from the order and generation position-dependent divergence of harmonics.Even small amounts of driving field astigmatism may result in cross-like patterns,coming from the superposition of individual harmonics with spatial profiles elongated in different directions.By correcting the aberrations using a deformable mirror,we show that fine-tuning the driving wavefront is essential for optimal spatial quality of the harmonics.

Optimizing an interleaved p-n junction to reduce energy dissipation in silicon slow-light modulators

Reducing power dissipation in electro-optic modulators is a key step for widespread application of silicon photonics to optical communication.In this work,we design Mach–Zehnder modulators in the silicon-on-insulator platform,which make use of slow light in a waveguide grating and of a reverse-biased p-n junction with interleaved contacts along the waveguide axis.After optimizing the junction parameters,we discuss the full simulation of the modulator in order to find a proper trade-off among various figures of merit,such as modulation efficiency,insertion loss,cutoff frequency,optical modulation amplitude,and dissipated energy per bit.Comparison with conventional structures(with lateral p-n junction and/or in rib waveguides without slow light)highlights the importance of combining slow light with the interleaved p-n junction,thanks to the increased overlap between the travelling optical wave and the depletion regions.As a surprising result,the modulator performance is improved over an optical bandwidth that is much wider than the slow-light bandwidth.

High-speed integrated QKD system

Quantum key distribution(QKD)is nowadays a well-established method for generating secret keys at a distance in an information-theoretically secure way,as the secrecy of QKD relies on the laws of quantum physics and not on computational complexity.In order to industrialize QKD,low-cost,mass-manufactured,and practical QKD setups are required.Hence,photonic and electronic integration of the sender's and receiver's respective components is currently in the spotlight.Here we present a high-speed(2.5 GHz)integrated QKD setup featuring a transmitter chip in silicon photonics allowing for high-speed modulation and accurate state preparation,as well as a polarization-independent low-loss receiver chip in aluminum borosilicate glass fabricated by the femtosecond laser micromachining technique.Our system achieves raw bit error rates,quantum bit error rates,and secret key rates equivalent to a much more complex state-of-the-art setup based on discrete components[A.Boaron et al.,Phys.Rev.Lett.121,190502(2018)].