A 5-mm piezo-scanning fiber device for high speed ultrafast laser microsurgery

Abstract

Towards developing precise microsurgery tools for the clinic, we previously developed image-guided miniaturized devices using low repetition rate amplified ultrafast lasers for surgery. To improve the speed of tissue removal while reducing device diameter, here we present a new 5-mm diameter device that delivers high-repetition rate laser pulses for high speed ultrafast laser microsurgery. The device consists of an air-core photonic bandgap fiber (PBF) for the delivery of high energy pulses, a piezoelectric tube actuator for fiber scanning, and two aspheric lenses for focusing the light. Its inline optical architecture provides easy alignment and substantial size reduction to 5 mm diameter as compared to our previous MEMS-scanning devices while realizing improved intensity squared (two-photon) lateral and axial resolutions of 1.16 μm and 11.46 μm, respectively. Our study also sheds light on the maximum pulse energies that can be delivered through the air-core PBF and identifies cladding damage at the input facet of the fiber as the limiting factor. We have achieved a maximum energy delivery larger than 700 nJ at 92% coupling efficiency. An in depth analysis reveals how this value is greatly affected by possible slight misalignments of the beam during coupling and the measured small beam pointing fluctuations. In the absence of these imperfections, self-phase modulation becomes the limiting factor for the maximum energy delivery, setting the theoretical upper bound to near 2 μJ for a 1-m long, 7-μm, air-core PBF. Finally, the use of a 300 kHz repetition rate fiber laser enabled rapid ablation of 150 µm x 150 µm area within only 50 ms. Such ablation speeds can now allow the surgeons to translate the surgery device as fast as ~4 mm/s to continuously remove a thin layer of a 150 µm wide tissue. Thanks to a high optical transmission efficiency of the in-line optical architecture of the device and improved resolution, we could successfully perform ablation of scarred cheek pouch tissue, drilling through a thin slice. With further development, this device can serve as a precise and high speed ultrafast laser scalpel in the clinic.

Lensless two-photon imaging through a multicore fiber with coherence-gated digital phase conjugation

“…1 The compatibility between multiphoton imaging and biology is well-known and a few endoscopic devices have been developed as a result. [7][8][9][10] Endoscopic devices for two-photon fluorescence (TPF) imaging generally utilize a single-mode fiber for pulse delivery with mechanical components encased in a probe at the fiber's distal tip to enable point scanning. [8][9][10] The scanning mechanism significantly increases the size of the endoscope over that of the light-delivering fiber.…”

“…[7][8][9][10] Endoscopic devices for two-photon fluorescence (TPF) imaging generally utilize a single-mode fiber for pulse delivery with mechanical components encased in a probe at the fiber's distal tip to enable point scanning. [8][9][10] The scanning mechanism significantly increases the size of the endoscope over that of the light-delivering fiber. Although these devices are a significant improvement over existing technologies, a more compact TPF endoscope remains a desired goal.…”

Development of tunable miniature piezoelectric-based scanners validated by the combination of two scanners in a direct image relay technique

“…For example, miniature PZTs have been utilized in endomicroscopy to provide widefield full-color imaging, 6 three-dimensional (3-D) optical coherence tomography imaging, 7,8 two-photon fluorescence imaging, 9 confocal imaging, 10 and to increase the ablation region of laser surgical probes. 11 Confined to a few millimeters in diameter (between 2.7 to 4 mm in middle-ear probes 12 and typically <5 mm for endomicroscopic systems), these probes typically consist of a miniature lens to focus light onto a PZT-controlled optical fiber, which is vibrated at its resonance frequency in order to image an area as defined by the actuator deflection, fiber mechanical properties, and imaging optics. The image reconstruction strategy, algorithm, and technique depend on the imaging modality employed by the scanner.…”

Design and Fabrication of Miniature Objective Lens for Laser Ablation Surgery Probe

“…A common limitation for these systems, however, is difficulty in delivering the light from the laser due to bulky equipment, which limits accessibility [4,5]. Miniature optics and optical fibers improve the flexibility of laser ablation systems, allowing for rapid surgeries of regions that are traditionally difficult to reach.…”

“…Miniature optics and optical fibers improve the flexibility of laser ablation systems, allowing for rapid surgeries of regions that are traditionally difficult to reach. The use of piezo-scanned fibers to deliver high-repetition rate amplified femtosecond lasers has been shown to reduce the time per cut while maintaining a miniature package [5]. By instead utilizing a custom objective in conjunction with a piezo-scanner, more light can be coupled from the laser, providing a larger cutting region for precision surgery.…”