Mid-Infrared ultra-high-Q resonators based on fluoride crystalline materials

Decades ago, the losses of glasses in the near infrared (near-IR) were investigated in views of developments for optical telecommunications. Today, properties in the mid-infrared (mid-IR) are of interest for molecular spectroscopy applications. In particular, high-sensitivity spectroscopic techniques based on high-finesse mid-IR cavities hold high promise for medical applications. Due to exceptional purity and low losses, whispering gallery mode microresonators based on polished alkaline earth metal fluoride crystals (i.e the $\mathrm{XF_2}$ family, where X $=$ Ca, Mg, Ba, Sr,...) have attained ultra-high quality (Q) factor resonances (Q$>$10$^{8}$) in the near-IR and visible spectral ranges. Here we report for the first time ultra-high Q factors in the mid-IR using crystalline microresonators. Using an uncoated chalcogenide (ChG) tapered fiber, light from a continuous wave quantum cascade laser (QCL) is efficiently coupled to several crystalline microresonators at 4.4 $\mu$m wavelength. We measure the optical Q factor of fluoride crystals in the mid-IR using cavity ringdown technique. We observe that $\mathrm{MgF_2}$ microresonators feature quality factors that are very close to the fundamental absorption limit, as caused by the crystal's multiphonon absorption (Q$\sim$10$^{7}$), in contrast to near-IR measurements far away from these fundamental limits. Due to lower multiphonon absorption in $\mathrm{BaF_2}$ and $\mathrm{SrF_2}$, we show that ultra-high quality factors of Q $\geqslant$ 1.4 $\times 10^{8}$ can be reached at 4.4 $\mu$m. This corresponds to an optical finesse of $\mathcal{F}>$4$\cdot$ 10$^{4}$, the highest value achieved for any type of mid-IR resonator to date, and a more than 10-fold improvement over the state-of-the-art. Such compact ultra-high Q crystalline microresonators provide a route for narrow linewidth frequency-stabilized QCL or mid-IR Kerr comb generation.Comment: C. Lecaplain and C. Javerzac-Galy contributed equally to this wor

The Boston University Photonics Center annual report 2009-2010

This repository item contains an annual report that summarizes activities of the Boston University Photonics Center for the period from July 2009 through June 2010. The report provides quantitative and descriptive information regarding photonics programs in education, interdisciplinary research, business innovation, and technology development. The Boston University Photonics Center (BUPC) is an interdisciplinary hub for education, research, scholarship, innovation, and technology development associated with practical uses of light.This report summarizes activities of the Boston University Photonics Center (BUPC) during the period July 2009 through June 2010. These activities span the Center’s complementary missions in education, research, technology development, and commercialization. In education, twenty-three BUPC graduate students received Ph.D. diplomas. BUPC faculty taught thirty-one photonics courses. Five graduate students were funded through the Photonics Fellowship Program. BUPC supported a Research Experiences for Undergraduates (REU) site in Photonics, which hosted summer interns in a ten-week program. Each REU student presented their research results to a panel of faculty and graduate students. Professors Goldberg and Swan continued their work with K-12 student outreach programs. Professor Goldberg’s Boston Urban Fellows Project started its sixth year. Professor Swan’s collaborative Four Schools for Women in Engineering program entered its third year. For more on our education programs, turn to the Education section on page 67. In research, BUPC faculty published journal papers spanning the field of photonics. Twelve patents were awarded to faculty this year for new innovations in the field. A number of awards for outstanding achievement in education and research were presented to BUPC faculty members. These honors include NSF CAREER Awards for Professors Altug, Dal Negro and Reinhard. New external grant funding for the 2009-2010 fiscal year totaled $21.1M, including$4.0M through a Cooperative Agreement with the U.S. Army Research Laboratory (ARL). For more information on our research activities, turn to the Research section on page 24. In technology development, the Department of Defense (DoD) continued to support the COBRA prototype systems. These photonics-technologies were pioneered by BUPC faculty and staff and have been deployed for field test and use at the United States Army Medical Research Institute for Infectious Diseases. New technology development projects for nuclear weapon detection, biodosimetry and terahertz imaging were launched and previously developed technologies for bacterial and viral sensing advanced toward commercial transition. For more information on our technology development pipeline and projects, turn to the Technology Development section on page 54. In commercialization, the business incubator continues to operate at capacity. Its tenants include more than a dozen technology companies with core business interests primarily in photonics and life sciences. It houses several companies founded by current and former BU faculty and students and provides students with an opportunity to assist, observe, and learn from start-up companies. For more information about business incubator activities, turn to the Business Incubation chapter in the Facilities and Equipment section on page 84. In early 2010, the BUPC unveiled a five-year strategic plan as part of the University’s comprehensive review of centers and institutes. The BUPC strategic plan will enhance the Center’s position as an international leader in photonics research. For more information about the strategic plan, turn to the BUPC Strategic Plan section on page 8

Fabrication and characterization of high-contrast mid-infrared GeTe₄ channel waveguides

We report the fabrication and characterization of high index contrast (Δn ~ 0.9) GeTe4 channel waveguides on ZnSe substrate for evanescent-field based biosensing applications in the mid-infrared spectral region. GeTe4 films were deposited by RF sputtering and characterized for their structure, composition, transparency and dispersion. The lift-off technique was used to pattern the waveguide channels. Waveguiding between 2.5-3.7 µm and 6.4-7.5 µm was demonstrated and mode intensity profile and estimated propagation losses are given for the 3.5 µm wavelength

The Boston University Photonics Center annual report 2015-2016

This repository item contains an annual report that summarizes activities of the Boston University Photonics Center in the 2015-2016 academic year. The report provides quantitative and descriptive information regarding photonics programs in education, interdisciplinary research, business innovation, and technology development. The Boston University Photonics Center (BUPC) is an interdisciplinary hub for education, research, scholarship, innovation, and technology development associated with practical uses of light.This has been a good year for the Photonics Center. In the following pages, you will see that this year the Center’s faculty received prodigious honors and awards, generated more than 100 notable scholarly publications in the leading journals in our field, and attracted $18.9M in new research grants/contracts. Faculty and staff also expanded their efforts in education and training, and cooperated in supporting National Science Foundation sponsored Sites for Research Experiences for Undergraduates and for Research Experiences for Teachers. As a community, we emphasized the theme of “Frontiers in Plasmonics as Enabling Science in Photonics and Beyond” at our annual symposium, hosted by Bjoern Reinhard. We continued to support the National Photonics Initiative, and contributed as a cooperating site in the American Institute for Manufacturing Integrated Photonics (AIM Photonics) which began this year as a new photonics-themed node in the National Network of Manufacturing Institutes. Highlights of our research achievements for the year include an ambitious new DoD-sponsored grant for Development of Less Toxic Treatment Strategies for Metastatic and Drug Resistant Breast Cancer Using Noninvasive Optical Monitoring led by Professor Darren Roblyer, continued support of our NIH-sponsored, Center for Innovation in Point of Care Technologies for the Future of Cancer Care led by Professor Cathy Klapperich, and an exciting confluence of new grant awards in the area of Neurophotonics led by Professors Christopher Gabel, Timothy Gardner, Xue Han, Jerome Mertz, Siddharth Ramachandran, Jason Ritt, and John White. Neurophotonics is fast becoming a leading area of strength of the Photonics Center. The Industry/University Collaborative Research Center, which has become the centerpiece of our translational biophotonics program, continues to focus onadvancing the health care and medical device industries, and has entered its sixth year of operation with a strong record of achievement and with the support of an enthusiastic industrial membership base