Publisher's Note: This paper, originally published on 2 July 2019, was replaced with a corrected/revised version on 3 August 2020. If you downloaded the original PDF but are unable to access the revision, please contact SPIE Digital Library Customer Service for assistance.
We here report an optical system for live 3D microscopy that we call the Multifocus 25-camera microscope (M25). M25 is a new design for aberration-corrected multifocus microscopy (MFM) that employs the latest generation of small, fast and sensitive CMOS cameras. Each of the 25 focal planes is captured on one of the individual cameras, enabling truly simultaneous 3D recording at >100Hz. M25 is built from a combination of custom manufactured diffractive Fourier optics elements and off-the-shelf components. We are employing M25 to study neural circuit function in small model organisms including C. elegans, Drosophila, and fish.
We have developed three light-based educational outreach activities targeted towards pre-university students, emphasizing experiential hands-on components for core learning via challenges the students must complete. These activities leverage photonics concepts from two active research areas at the Univ. of California Santa Barbara: integrated optics and solid-state lighting. The activities center on (1) building a free-space optical link, (2) subtractive and additive color mixing, and (3) guiding light using gelatin waveguides. These activities are self-contained that is, the necessary background and intuition are introduced and built, respectively, before culminating in the main demonstration. The color-mixing and gelatin waveguide activities were designed for middle school students (ages 10-13) and their families, while the free-space optical link activity was designed for high school students (ages 14-18). Graduate students, not necessarily in photonics or optics, typically lead these activities for groups of 20-30 students after an initial training. We have found that we are able to garner considerable excitement from students when activities culminate in a challenge, especially if it has a competitive nature. This allows leaders to emphasize important practices in scientific research, such as: using the success of others' experiments to one's benefit, making informed hypotheses and testing them, persistence in understanding and solving a problem, and finally, the desire to improve upon a working solution.
Since the first demonstration of swept source optical coherence tomography (SS-OCT) imaging using widely tunable micro-electromechanical systems vertical cavity surface-emitting lasers (MEMS-VCSELs) in 2011, VCSEL-based SSOCT has advanced in both device and system performance. These advances include extension of MEMS-VCSEL center wavelength to both 1060nm and 1300nm, improved tuning range and tuning speed, new SS-OCT imaging modes, and demonstration of the first electrically pumped devices. Optically pumped devices have demonstrated continuous singlemode tuning range of 150nm at 1300nm and 122nm at 1060nm, representing a fractional tuning range of 11.5%, which is nearly a factor of 3 greater than the best reported MEMS-VCSEL tuning ranges prior to 2011. These tuning ranges have also been achieved with wavelength modulation rates of >500kHz, enabling >1 MHz axial scan rates. In addition, recent electrically pumped devices have exhibited 48.5nm continuous tuning range around 1060nm with 890kHz axial scan rate, representing a factor of two increase in tuning over previously reported electrically pumped MEMS-VCSELs in this wavelength range. New imaging modes enabled by optically pumped devices at 1060nm and 1300nm include full eye length imaging, pulsatile Doppler blood flow imaging, high-speed endoscopic imaging, and hand-held wide-field retinal imaging.
In the last 2 years, the field of micro-electro-mechanical systems tunable vertical cavity surface-emitting lasers (MEMS-VCSELs)
has seen dramatic improvements in laser tuning range and tuning speed, along with expansion into unexplored
wavelength bands, enabling new applications. This paper describes the design and performance of high-speed ultra-broad
tuning range 1050nm and 1310nm MEMS-VCSELs for medical imaging and spectroscopy. Key results include
achievement of the first MEMS-VCSELs at 1050nm and 1310nm, with 100nm tuning demonstrated at 1050nm and
150nm tuning at shown at 1310nm. The latter result represents the widest tuning range of any MEMS-VCSEL at any
wavelength. Wide tuning range has been achieved in conjunction with high-speed wavelength scanning at rates beyond 1
MHz. These advances, coupled with recent demonstrations of very long MEMS-VCSEL dynamic coherence length,
have enabled advancements in both swept source optical coherence tomography (SS-OCT) and gas spectroscopy.
VCSEL-based SS-OCT at 1050nm has enabled human eye imaging from the anterior eye through retinal and choroid
layers using a single instrument for the first time. VCSEL-based SS-OCT at 1310nm has enabled real-time 3-D SS-OCT
imaging of large tissue volumes in endoscopic settings. The long coherence length of the VCSEL has also enabled, for
the first time, meter-scale SS-OCT applicable to industrial metrology. With respect to gas spectroscopy, narrow dynamic
line-width has allowed accurate high-speed measurement of multiple water vapor and HF absorption lines in the 1310nm
wavelength range, useful in gas thermometry of dynamic combustion engines.