This award supports the purchase of a Coherent MBR-110 titanium:sapphire(Ti:S) continuous-wave laser, with accompanying pump laser, optical table, and diagnostic equipment, for use in ultracold atomic physics, quantum information science with diamond nitrogen-vacancy centers, and injection dynamics of vertical-cavity surface-emitting lasers. Prof. Lundblad will use ultracold atoms loaded from a Bose-Einstein condensate into an optical lattice to explore systems which simulate or behave analogously to poorly-understood condensed-matter systems, e.g. those involved with high-Tc superconductivity and quantum magnetism. Building on previous experience with double-well lattices and spin-dependent lattices, he will explore strongly-correlated many-body physics in lattices of nonstandard geometry and topology: the triangle and honeycomb lattices, and radiofrequency-dressed lattices with ring-like single-site wavefunctions. Prof. Childress will study the nitrogen-vacancy (NV) defect center in diamond as a leading system for quantum information science. In particular, the NV spin degree of freedom is a versatile single spin system readily prepared, controlled, and detected with optical and microwave excitation. She will use stimulated-emission depletion (STED) techniques for subwavelength imaging methods in a homebuilt confocal apparatus, exploiting the natural advantages of STED used with individual NV centers. The research also centers on an improved understanding of NV spin dynamics under conditions necessary for STED-based imaging. Prof. Lin will use the equipment to study injection dynamics in vertical-cavity surface-emitting lasers (VCSELs), specifically aiming to understand the nonlinear dynamics of optical injection in the multimode regime, with an eye towards applications in chaos-based secure communication via VCSEL synchronization. The particular features of the Ti:S laser system - multiwatt power, 300nm tuning capability, and sub-100-kHz spectral purity - enables all of the investigators' research goals.
The acquisition of the Ti:S laser system has a broad impact on undergraduate research and education at Bates as well as on local, state, and national research infrastructure. Undergraduate research is a core component of the science curriculum at Bates, experienced through independent study, summer research apprenticeships, and a required senior thesis project. These research experiences are crucial to Bates' role in sending a disproportionately large number of students into postgraduate study in the sciences - the pipeline that provides the trained individuals necessary for technological and economic development. In addition to the three investigators named in this proposal, the requested laser system will be used by six to twelve undergraduate researchers each year, and potentially by more via curricular use. The laser system is important to the research activity of the faculty involved, resulting in increased scholarly activity, collaboration with other institutions, and statewide and national exposure of scientific work being performed at Bates. The institutional commitment to research at Bates in combination with extramural funding allow Bates faculty to operate at a high level of scholarly activity, and the on-site presence of state-of-the-art instrumentation ensures that this activity will continue unabated. The equipment thus impacts Bates students (many of whom are members of underrepresented groups) both through direct use of the apparatus through research, and through broad exposure to an active, vibrant, well-equipped research environment.
The PI recently completed acquisition of a laser system through the NSF Major Research Instrumentation program. Final assembly of the facility was delayed by manufacturer supply-chain issues, but the PI anticipates achieving user-ready status by the end of calendar 2012. The Solstis laser system (manufactured by M-Squared Lasers, Glasgow, Scotland) is a high-performance and ultra-stable tunable continuous-wave (cw) Ti:S laser. Ti:S refers to the lasing medium: a crystal of sapphire (Al2O3) that has been doped with titanium ions. The laser is built in a ring configuration, and as is typical of all Ti:S lasers, is tunable over hundreds of nanometers: given the particular pump laser, we possess tunability in the range 700--950 nm, with some ability to push outside that range with factory modification. Ti:S lasers are typically pumped by green light; argon-ion lasers at 514.5 nm have been used historically, but have largely been replaced by frequency-doubled solid-state lasers at 532 nm. We use a pump laser provided by the leader in the field, Coherent Inc.; in order to maximize Ti:S output the highest available pump power is used, specifically, the model Verdi V18 providing in excess of 18W. When pumped by the V18, the Solstis outputs over 4W at peak wavelength near 800 nm. The PI's use of this instrument largely revolves around the creation of optical lattices: interference patterns of light that serve as periodic potential surfaces for trapped ultracold atoms through the optical dipole force, whereby atoms seek out regions of higher or lower intensity depending on the trapping laser wavelength and polarization. Co-PI Prof. Lin will use the equipment to study injection dynamics in vertical-cavity surface-emitting lasers (VCSELs), specifically aiming to understand the nonlinear dynamics of optical injection. Prior to her departure, Prof. Childress had planned to use the laser facility to study the quantum-information applications of the nitrogen-vacancy (NV) center in diamond. We anticipate a high likelihood that the tenure-track hire will be able to make use of the laser facility, as the hiring of an experimentalist in the condensed-matter or AMO fields is a department priority. The acquisition of this laser system has already had impacts on the department and on Bates, beginning primarily with training and involvement of students with the use of a cutting-edge instrument such as the Ti:S system. Each of the investigators involved traditionally mentors 2--3 students per year, as a supervisor of independent study, summer research, or work on a senior thesis. With the integration of this instrumentation into the various research projects in the department, more and more of those students will have access to direct training with this system, and will be able to use it to guide research projects that otherwise would be unavailable. Students have already been trained in the basic operation of the laser system, in particular beginning to learn how to couple the laser light into single-mode optical fibers, a task that while common in AMO laboratories involves considerable physics background and practical lab training. Acquisition of the equipment requested has allowed the department to significantly improve the research capabilities that are at the heart of this mentoring and education process. The Ti:S system may also find occasional curricular use both as a standalone module in our upper-division lab course, and as one of several lab modules for a potential senior-level laser physics course or independent study. The equipment thus impacts Bates students (including members of underrepresented groups) both through direct use of the apparatus through research, and through broad exposure to an active, vibrant, well-equipped research environment. The general characteristics of the system have also been disseminated to other departments (Chemistry, Biology) that represent possible future use of the system. The acquisition of this laser facility gives the PI and his department access to equipment that generally is only present at very-well-equipped research university labs, and raises the bar for what questions can be asked and what science can be done at an elite small liberal-arts college.
