Investigation of Laser Induced Breakdown Spectroscopy(LIBS)for the Differentiation of Nerve and Gland Tissue-A Possible Application for a Laser Surgery Feedback Control Mechanism

Laser surgery provides clean,fast and accurate modeling of tissue.However,the inability to determine what kind of tissue is being ablated at the bottom of the cut may lead to the iatrogenic damage of structures that were meant to be preserved.In this context,nerve preservation is one of the key challenges in any surgical procedure.One example is the treatment of parotid gland pathologies,where the facial nerve（N.VII） and its main branches run through and fan out inside the glands parenchyma.A feedback system that automatically stops the ablation to prevent nerve-tissue damage could greatly increase the applicability and safety of surgical laser systems.In the present study,Laser Induced Breakdown Spectroscopy（LIBS） is used to differentiate between nerve and gland tissue of an ex-vivo pig animal model.The LIBS results obtained in this preliminary experiment suggest that the measured spectra,containing atomic and molecular emissions,can be used to differentiate between the two tissue types.The measurements and differentiation were performed in open air and under normal stray light conditions.

Optical prediction of single muscle fiber force production using a combined biomechatronics and second harmonic generation imaging approach

Skeletal muscle is an archetypal organ whose structure is tuned to match function.The magnitude of order in muscle fibers and myofibrils containing motor protein polymers determines the directed force output of the summed force vectors and,therefore,the muscle’s power performance on the structural level.Structure and function can change dramatically during disease states involving chronic remodeling.Cellular remodeling of the cytoarchitecture has been pursued using noninvasive and label-free multiphoton second harmonic generation(SHG)microscopy.Hereby,structure parameters can be extracted as a measure of myofibrillar order and thus are suggestive of the force output that a remodeled structure can still achieve.However,to date,the parameters have only been an indirect measure,and a precise calibration of optical SHG assessment for an exerted force has been elusive as no technology in existence correlates these factors.We engineered a novel,automated,high-precision biomechatronics system into a multiphoton microscope allows simultaneous isometric Ca2+-graded force or passive viscoelasticity measurements and SHG recordings.Using this MechaMorph system,we studied force and SHG in single EDL muscle fibers from wt and mdx mice;the latter serves as a model for compromised force and abnormal myofibrillar structure.We present Ca2+-graded isometric force,pCa-force curves,passive viscoelastic parameters and 3D structure in the same fiber for the first time.Furthermore,we provide a direct calibration of isometric force to morphology,which allows noninvasive prediction of the force output of single fibers from only multiphoton images,suggesting a potential application in the diagnosis of myopathies.

Step-size selection for split-step based nonlinear compensation with coherent detection in 112-Gb/s 16-QAM transmission

Non-uniform step-size distribution is implemented for split-step based nonlinear compensation in singlechannel 112-Gb/s 16 quadrature amplitude modulation （QAM） transmission. Numerical simulations of the system including a 20 × 80 km uncompensated link are performed using logarithmic step size distribution to compensate signal distortions. 50% of reduction in number of steps with respect to using constant step sizes is observed. The performance is further improved by optimizing nonlinear calculating position （NLCP） in case of using constant step sizes while NLCP optimization becomes unnecessary when using logarithmic step sizes, which reduces the computational effort due to uniformly distributed nonlinear phase for all successive steps.

On-chip beam rotators,adiabatic mode converters,and waveplates through low-loss waveguides with variable cross-sections

Photonics integrated circuitry would benefit considerably from the ability to arbitrarily control waveguide cross-sections with high precision and low loss,in order to provide more degrees of freedom in manipulating propagating light.Here,we report a new method for femtosecond laser writing of optical-fiber-compatible glass waveguides,namely spherical phase-induced multicore waveguide(SPIM-WG),which addresses this challenging task with three-dimensional on-chip light control.Fabricating in the heating regime with high scanning speed,precise deformation of cross-sections is still achievable along the waveguide,with shapes and sizes finely controllable of high resolution in both horizontal and vertical transversal directions.We observed that these waveguides have high refractive index contrast of 0.017,low propagation loss of 0.14 dB/cm,and very low coupling loss of 0.19 dB coupled from a single-mode fiber.SPIM-WG devices were easily fabricated that were able to perform on-chip beam rotation through varying angles,or manipulate the polarization state of propagating light for target wavelengths.We also demonstrated SPIM-WG mode converters that provide arbitrary adiabatic mode conversion with high efficiency between symmetric and asymmetric nonuniform modes;examples include circular,elliptical modes,and asymmetric modes from ppKTP(periodically poled potassium titanyl phosphate)waveguides which are generally applied in frequency conversion and quantum light sources.Created inside optical glass,these waveguides and devices have the capability to operate across ultra-broad bands from visible to infrared wavelengths.The compatibility with optical fiber also paves the way toward packaged photonic integrated circuitry,which usually needs input and output fiber connections.