Abstract We report an experimental study on the interaction of optical vortex (OV) beams with water and biological tissues, highlighting their potential for photonics--based biomedical applications. By varying the topological charge or orbital angular momentum (OAM) of the OV beam, we observe that higher-order vortex beams exhibit improved transmission through turbid media and induce stronger photothermal responses in pork tissue. The results demonstrate a clear order-dependent relationship between beam structure and light--tissue interaction. Moreover, we investigate the enhancement of heat generation in pork samples using the vortex beam in combination with the Talbot pattern. An increase in temperature of 0.44 o C for l = 0 and 1.02 o C for l = 3 was observed. The results show a significant improvement in heating efficiency when the Talbot pattern is employed. Although the temperature rise depends on the characteristics and thickness of the pork tissue, a consistently higher temperature increase was observed for optical vortex beams with higher OAM orders when combined with the Talbot effect, compared with lower-order or Gaussian illumination under the investigated conditions. These findings not only provide fundamental insights into the propagation of structured light in scattering media but also suggest new opportunities for enhancing laser therapy, photothermal treatment, and deep-tissue biomedical imaging.
As the mid-infrared range finds increasing interest in numerous applications, the demand for integrated optical components operating at these wavelengths is becoming even more critical. In this work, we present a novel method for fabricating 1 $\times$ 2 beam splitters with precisely controlled power distribution among the two output arms. The devices are realized using femtosecond laser writing in chalcogenide glass and the output power balance is tuned by inducing refractive index variations ( $\Delta n$ ) of different magnitudes in the splitting region of each arm. The power ratio between the two outputs can be continuously adjusted from 50:50 to 95:5 without introducing additional losses. The components are evaluated at a wavelength of 4.5 $\mu$ m, but measurements using a supercontinuum source show that the coupling ratio remains constant over an unprecedented spectral range exceeding 1 $\mu$ m. Finally, these results are extended to three-dimensional components with the fabrication of a 1 $\times$ 6 splitter featuring controlled power distribution across the output arms.
Abstract On-chip label-free detection of microparticles is a key challenge for developing miniaturized platforms for real-time sensing in liquids. A promising strategy involves exploiting photoacoustic and thermoelastic effects to convert optical absorption into detectable acoustic signals. Understanding these processes at the single-particle level is essential for advancing next-generation diagnostic and analytical platforms. In this work, we present a numerical investigation of the thermal, mechanical, and acoustic dynamics of a dye-free polystyrene microsphere in water under pulsed optical excitation. We developed a fully coupled finite-element model to simulate heat transfer, thermoelastic deformation, and acoustic wave propagation. The effect of optical pulse duration, from nanoseconds to milliseconds, was systematically analysed. This provides a crucial link between the temporal profile of the photonic excitation and the resulting optomechanical response. Simulations reveal a transition from an impulsive thermoelastic regime for nanosecond pulses, characterized by elastic ringing, to a quasi-static regime for longer pulses. While near-field pressure depends on pulse duration, far-field propagation becomes largely independent of excitation conditions due to acoustic attenuation in water. These findings offer key design rules for tailoring laser source specifications to optimize energy conversion efficiency. Ultimately, this work establishes a comprehensive predictive framework for the development of integrated on-chip photonics and photoacoustic sensing architectures.
High-speed vertical-cavity surface-emitting lasers (VCSELs) and their arrays are essential for enhancing bandwidth density while minimizing energy consumption per bit in near-packaged or co-packaged optics (NPO or CPO) modules for modern AI networks. In this paper, we demonstrate that incorporating optimized Zn-diffusion ring-shaped apertures with 850 and 1064 nm VCSEL cavities for single-mode (SM) output significantly improves slope and modulation efficiencies while preserving low RIN. Compared with multi-mode reference devices without Zn-diffusion apertures, these VCSELs achieve clear eye–opening at much lower pre-bias currents and smaller peak-to-peak RF driving-voltages ( V _pp ). For the 850 nm VCSEL, clear eye–opening can be achieved at 100 Gbit s ^−1 with the PAM-4 modulation format under a low bias current of 4 mA, a small EDR (100 fJ bit ^−1 ), and a record low V _pp as 0.35 V. The 1060 nm VCSEL exhibits superior high-temperature performance compared to the SM reference device using the conventional circular Zn-diffusion aperture. It obtains error-free 32 Gbit s ^−1 on-off-keying transmission at 125 $^ \circ {\text{C}}$ with a V _pp as low as 0.28 V, without requiring power-consuming retiming DSP ICs.
