Optical design and imaging performance testing of a 96-mm diameter femtosecond laser microsurgery probe

Abstract

We present the optical design of a 9.6-mm diameter fiber-coupled probe for combined femtosecond laser microsurgery and nonlinear optical imaging. Towards enabling clinical use, we successfully reduced the dimensions of our earlier 18-mm microsurgery probe by half, while improving optical performance. We use analytical and computational models to optimize the miniaturized lens system for off-axis scanning aberrations. The optimization reveals that the optical system can be aberration-corrected using simple aspheric relay lenses to achieve diffraction-limited imaging resolution over a large field of view. Before moving forward with custom lenses, we have constructed the 9.6-mm probe using off-the-shelf spherical relay lenses and a 0.55 NA aspheric objective lens. In addition to reducing the diameter by nearly 50% and the total volume by 5 times, we also demonstrate improved lateral and axial resolutions of 1.27 µm and 13.5 µm, respectively, compared to 1.64 µm and 16.4 µm in our previous work. Using this probe, we can successfully image various tissue samples, such as rat tail tendon that required 2-3 × lower laser power than the current state-of-the-art. With further development, image-guided, femtosecond laser microsurgical probes such as this one can enable physicians to achieve the highest level of surgical precision anywhere inside the body.

Exploring nonlinear pulse propagation, Raman frequency conversion and near octave spanning supercontinuum generation in atmospheric air-filled hollow-core Kagomé fiber

“…During the last decade, demonstration of high peak power pulsed lasers operating in the GW range with high repetition rates in a commercial tabletop form has allowed development of novel applications in, for example, micro-machining 1 , micro-surgery 2 and biophotonics 3 . However, the ultra-high peak power characteristics of these lasers creates the problem of delivering such pulses in a flexible and reliable way.…”

Optimized inhibited-coupling Kagome fibers at Yb-Nd:Yag (85 dB/km) and Ti:Sa (30 dB/km) ranges

“…Furthermore, this power and energy handling has been demonstrated with the most commonly used USP lasers, such as those based on Yb or Nd:Yag [8,9], on Ti:Sapphire (Ti:Saph) [10], or on frequency-doubled Yb [11] or Er [12]. Finally, any improvement in the transmission performance of these fibers will further improve the growing and spreading use of USP lasers in industrial applications as various as biophotonics [13], micro-machining [14] and micro-surgery [15].…”

MEMS-based multiphoton endomicroscope for repetitive imaging of mouse colon

“…Fu et al reported a 5 mm diameter instrument with 10 µm axial resolution using a 2D mirror based on electrothermal actuation [8]. Fluorescence images were collected ex vivo from rat colon using raster scanning with individual frames collected at 7 lines per sec, a speed that is too slow for in vivo imaging.…”

“…Alternatively, beam scanning can be performed using tiny mirrors developed with microelectromechanical systems (MEMS) technology. MEMS scanners have been developed previously [7][8][9], but the overall size of the endomicroscope was not adequately small to perform repetitively imaging in mice. We aim to demonstrate a handheld multiphoton endomicroscope with a small distal diameter of 3.4 mm using a compact high speed MEMS scanner to perform repetitive imaging in the colon of a live mouse with "histology-like" performance.…”