The design, fabrication, assembly, and characterization of a miniature adjustable-focus camera module driven by MEMS-thermal actuators are presented. The camera module consists of one solid tunable lens for optical power variation, two identical MEMS-thermal actuators integrated with displacement amplifiers for lens element driving, a CMOS image sensor for recording, and necessary CNC fabricated components for supporting and housing. Fully 3D-multiphysics simulations with valid material properties are performed to explore the design and, hence, optimize the performance of the system. In this paper, the fabricated MEMS-devices are clearly demonstrated, and followed by the detailed characterization of the camera module. Static characterizations of the system, including the temperature distribution on actuators, electric resistance change with temperature increase, displacement-voltage curve of actuator, and the focal length tuning capability, are tested. Dynamic response speed and imaging performance of the camera module are also covered. Results show that the designed MEMS actuator is able to provide a maximum output displacement of 135 μm when a 10 V driving voltage is applied. Driven by the thermal actuator, the solid tunable lens presents a repeatable focal length tuning from 9.2 to 7.9 mm with precise focus control. The adjustable-focus capability of the miniature camera module is experimentally demonstrated by clearly focusing targets placed at different object distances.

This paper presents the design, simulation, fabrication, assembly, and testing of a miniature thermo-pneumatic optofluidic lens. The device comprises two separate zones for air heating and fluid pressing on a flexible membrane. A buried three-dimensional spiral microchannel connects the two zones without pumps or valves. The three-dimensional microfluidic structure is realized using a high-resolution three-dimensional printing technique. Multi-physics finite element simulations are introduced to assess the optimized air chamber design and the low-temperature gradient of the optical liquid. The tunable lens can be operated using a direct-current power supply. The temperature change with time is measured using an infrared thermal imager. The focal length ranges from 5 to 23 mm under a maximum voltage of 6 V. Because of the small size and robust actuation scheme, the device can potentially be integrated into miniature micro-optics devices for the fine-tuning of focal lengths.

The design and fabrication of a novel bidirectionally optofluidic tunable microlens actuated by thermoelectric coolers (TECs) are reported. A high-resolution three-dimensional printing technology is adopted to fabricate the truly three-dimensional structure of an optofluidic chip. Owing to the bidirectional thermal property of the TECs, both upward and downward membrane profiles are available under the control of a programmable direct-current power supply. The focal length of the liquid lens decreases from 25 to 5mm as the voltage is increased from 0.2 to 1.1V whereas the focal length changes from -25 to -5mm as the current is applied in the opposite direction. A finite element simulation with COMSOL software is conducted to assess the temperature distribution on the device. The response functions of the TECs are investigated for the heating and cooling processes, and the imaging properties are characterized.

Post-compression based on self-phase modulation (SPM) is widely used for femtosecond pulse shortening. However, the influence of the driving beam wavefront on different compression schemes remains unexplored. Using a Yb-doped fiber laser (230 fs, 200 kHz), we experimentally compare pulse compression in a hollow-core fiber (HCF) and a multi-pass cell (MPC). The HCF compresses pulses to 27 fs with an efficiency of approximately 55% and improves beam quality via modal filtering. The MPC achieves 34 fs pulses with an efficiency of approximately 90% and exhibits a quasi-waveguide mode-filtering effect, substantially enhancing output wavefront quality even when the input wavefront is poor. High-harmonic generation (HHG) experiments show that the HCF-driven source yields a higher photon flux (1.25 × 10¹¹ photons/s) compared to the MPC-driven source (4.95 × 10¹⁰ photons/s). Using a second Yb-doped fiber laser (223 fs, 100 kHz), a cascaded MPC–HCF scheme generates 7.5 fs pulses with an overall efficiency of approximately 70%, enabled by employing a larger-core HCF in the second compression stage. HHG experiments performed with the compressed pulses demonstrate that spatial phase evolution is a critical parameter in post-compression design for such applications.