Mark Cronin-Golomb

Tufts University | Tufts · Department of Biomedical Engineering

Controlling physicochemical properties of light-unresponsive drugs, by light, prima facie, a paradox approach. We expanded light control by ion pairing light-unresponsive salicylate or ibuprofen to photoswitchable azobenzene counterions, thereby reversibly controlling supramolecular structures, hence the drugs' physicochemical and kinetic propertie...

Azo dye modified Bombyx mori silkworm silk creates a photo-responsive ‘azosilk’ biomaterial, allowing 3-d laser patterning. Written regions fluoresce, and become fluid-filled raised ‘micro-blisters’, with a 10-fold photo-softening effect of the modulus. Patterning is facile and versatile, with potential applications as soft tunable materials for dy...

Biomechanics plays a central role in breast epithelial morphogenesis. In this study we have used 3D cultures in which normal breast epithelial cells are able to organize into rounded acini and tubular ducts, the main structures found in the breast tissue. We have identified fiber organization as a main determinant of ductal organization. While bulk...

Atomic force microscopes have become indispensable tools for mechanical characterization of nanoscale and submicron structures. However, materials with complex geometries, such as electrospun fiber networks used for tissue scaffolds, still pose challenges due to the influence of tension and bending modulus on the response of the suspended structure...

The chimeric proteins, silk-elastin-like protein polymers (SELPs), consist of repeating units of silk and elastin to retain the mechanical strength of silk, while incorporating the dynamic environmental sensitivity of elastin. A retinal-modified silk-elastin-like protein polymer was prepared, modified and studied for photodynamic responses. The pro...

In this study, we demonstrated that thin films of azobenzene-modified Bombyx mori silk showed optically induced effects similar to those found in other polymers incorporating azobenzene moieties. Optically induced anisotropy in refractive index reached 7 × 10−3 with 18 J cm−2 required to reach 50% of steady state. Holograms were formed with diffrac...

Electric fields are integral to many biological events, from maintaining cellular homeostasis to embryonic development to healing. The application of electric fields offers substantial therapeutic potential, while optimal dosing regimens and the underlying mechanisms responsible for the positive clinical impact are poorly understood. The purpose of...

We report a novel method for characterizing the stiffness of white light supercontinuum tweezers, in which the nonlinear photonic crystal fiber used for supercontinuum generation is also utilized as an effective confocal pinhole to track the motion of a trapped bead and as a scan head to realize rapid scanning of the optical trap. By measuring the...

In this paper, we report on gold nanoparticle (GNP) doped silk films as an implantable and degradable heating element activated by light, which can be potentially used for wireless powering of implanted microdevices. Proof-of-concept experiments have been conducted by casting a GNP doped silk film on a miniature thermal-power chip, which generates...

Contains table of contents for Part II, table of contents for Section 1, and reports on seven research projects.

We demonstrate photomechanical actuation by measuring the variation of the diffracted orders in a free-standing nanopatterned diazonium-modified silk fibroin film by modulating a blue excitation light source.

Azobenzene modified silk, a biocompatible material suitable for applications in biomedicine is shown to display photo-effects such as optically induced birefringence, suitability as a holographic recording material and photoinduction of surface relief features.

We demonstrate photomechanical actuation by measuring the variation of the diffracted orders in a free-standing nanopatterned diazonium-modified silk fibroin film by modulating a blue excitation light source.

We investigate numerically and experimentally all-optical control of particles inside water filled, silica, hollow-core photonic crystal fiber (HC-PCF). We use an optical trapping beam focused outside the fiber, through its microstructure, perpendicular to the HC-PCF and independent of the guided fiber core mode. Finite difference time domain simul...

The photorefractive effect and artificial Kerr effect are both drift and diffusion based nonlinearities. This paper treats them in a unified fashion and develops a formalism for the analysis of general nonlinearities of this type. The intensity dependence of the steady state and response time is discussed.

We propose the use of large bandwidth mid-IR supercontinuum coupled with machine learning algorithms could provide a solution to non-invasive glucose detection. The SC uses millimeters of non-linear optical fiber, lowering costs and enhancing compactness.

The ancient silk fiber finds resurgence in a new paradigm of highly functional optofluidic devices embodied by an active oxygenation sensor comprising a hemoglobin infused cast silk integrated diffraction grating for spectral analysis.

We numerically examine the trapping efficiency of an optical beam transmitted transversely through a hollow-core, water filled photonic crystal fiber. The trapping beam retains its structure and trapping efficiency despite the fiber microstructure.

We report broad bandwidth, mid-IR supercontinuum generation using a sub-cm (8 mm) length of highly nonlinear tellurite microstructured photonic crystal fiber (PCF). We pump the fiber at telecommunication wavelengths by using 1550 nm, 100 fs pulses of energy E=1.9 nJ. When coupled in the PCF, these pulses result in a supercontinuum (SC) bandwidth of...

Silk-based biomaterial systems have been previously explored for a variety of medical and nonmedical materials needs. The unique biophysical features of silks provide options to generate highly tailored structures and morphologies with this unique family of fibrous proteins. To exploit these features, we have optimized the all aqueous processing of...

We present the use of two-photon excited fluorescence and second harmonic generation, to monitor electric field effects on osteogenic differentiation of human mesenchymal stem cells in terms of cellular morphology, biochemical composition and collagen deposition.

We demonstrate an optofluidic lab-on-a-chip device by fabricating an optical transmission grating with an integrated microfluidic channel using soft lithography in polydimethylsiloxane. This integration of functionalities provides spectral analysis ldquoon-chiprdquo of the contents of the microfluidic channel. We demonstrate this functionality by p...

A rate equation approach is used to analyse four-wave mixing based on the optical gradient forces normally associated with optical tweezers.

The optical tweezers effect offers the potential for all-optical control of microfluidic and optofluidic devices. Several possible means for applying optical tweezers to optofluidics are described including the use of polymers to tether transversely trapped microspheres and eliminate the need for axial trapping. Also covered is the use of optically...

We present the tapering of photonic crystal fibers formed from SF6 glass to 400 nm core diameter. We generate supercontinuum in the tapers using pump pulse energies as low as 65 picojoules.

Tunable optical filters are fabricated in hollow core photonic crystal fibers by using optical tweezer beams directed transversely to the fiber to load and space silica microspheres in the fluid filled hollow core.

We demonstrate two-octave supercontinuum generation in an 8 cm length of tellurite glass photonic crystal fiber. The high modal confinement and nonlinearity of the tellurite PCF enables the short length of fiber used.

This article presents a simple and novel method for the fabrication of cylindrical microchannels in polymer or biopolymer substrates. This process results in highly regular, cylindrical microchannels, suitable both to the transport of liquid and the transmission of light. This method eliminates issues associated with positioning tolerances characte...

The miniaturization of optical devices and their in-tegration for creating adaptive and reconfigurable photonic inte-grated circuits requires effective platforms and methods to con-trol light over very short distances. We present here several tech-niques and objects that we have developed to harness light at the sub-micrometer scale. These new tool...

The integration of microfluidics and microphotonics brings the ability to tune and reconfigure ultra-compact optical devices. This flexibility is essentially provided by three characteristics of fluids that are scalable at the micron-scale: fluid mobility, large ranges of index modulation, and abrupt interfaces that can be easily reshaped. Several...

We present the concept of micro-electro-mechanical-systems actuated by optical trapping embodied by demonstrating a silica micro-cantilever (made from tapered optical fiber) under optical trap control. This platform also serves as a trap diagnostic

We explore the possibility of using optical tweezers to enable all optical control of optofluidic circuits. Optically trapped microspheres can be used as microlenses for optical signal switching and steering. By using cantilevers instead of microspheres we provide a method for robust and stable placement of switching elements in the optofluidic cir...

Cantilevers are commonly used in microelectromechanical systems for sensing and optical switching applications. The authors demonstrate the use of optical tweezers for all optical actuation of a tapered optical fiber used as a cantilever and to drive it as a micromechanical oscillator. A fiber optic confocal detection system is used to monitor back...

We introduce a new type of optical MEMS through an optical micro-fiber waveguide controlled using optical trapping. We also use the mechanical properties of the micro-fiber to measure properties of the optical trap.

We present a photonic band gap (PBG) structure (or nonlinear photonic crystal) design for terahertz (THz) wave parametric generation, whose component materials have a small refractive index difference in the near infrared and a large index difference for THz waves. The structural dispersion of such a PBG structure is strong in the THz range but neg...

We introduce a class of highly compact refractometers integrated onto a planar microfluidic geometry that demonstrates high resolution refractive index measurements in 50 μm fluid channels utilizing a Fabry–Perot cavity formed between resonant Bragg grating reflectors. This cavity forms a resonant peak in the transmission spectrum which is dependen...

We present a photonic band gap (PBG) structure design for terahertz (THz) wave parametric generation, which has crystal layer fabrication tolerance of a few micrometers and can be made with traditional polishing methods. This PBG structure consists of two component materials with a small refractive index difference at near infrared pump wavelengths...

We review progress in optofluidics performed using optical fibers as the photonic transport medium. We fluidically tune the transmission properties of microstructured optical fibers and use telecommunications fibers to probe the optical properties of fluids

In this paper, the authors demonstrated the use of optically trapped microspheres to tune the transmission properties of embedded fiber optic waveguides, and the use of optical tweezers for optical actuation of cantilevers for use as switches and sensors

The authors utilized optical trapping as a novel form of micro actuation, demonstrated using an optical micro-fiber that is trapped and spatially directed.

We demonstrate a liquid phase refractometer that utilizes fiber Bragg gratings integrated across planar microfluidic channels. We test the device using various concentrations of saline solution and report sensitivity to refractive index changes of 0.2%.

We introduce a novel method of attaining all-optical beam control in an optofluidic device by displacing an optically trapped micro-sphere though a light beam. The micro-sphere causes the beam to be refracted by various degrees as a function of the sphere position, providing tunable attenuation and beam-steering in the device. The device itself con...

Lambda DNA is used to tether polystyrene microspheres to an optical substrate, thus eliminating the need for high numerical aperture trapping lenses in single beam optical tweezers to provide axial trapping. The tethered particle may be used as a sensor probe to measure local viscosity and forces on the trapped particle such as those induced by flu...

Cascaded nonlinear optical interactions are analyzed for their potential to overcome quantum-defect related limitations on the efficiency of terahertz wave difference-frequency generation. The dispersion of ZnTe permits phase-matched production of a series of Stokes lines from two initial near-infrared beams. As the pump beams run down the Stokes l...

One dimensional photonic bandgap structures can be used to enhance the efficiency of nonlinear optical parametric processes. Structural dispersion can be used to achieve phase matching, and resonant effects can be used to increase the intensity of the pump beams in the nonlinear optical material. In this paper these ideas are used to derive for the...

We demonstrate, what is to the best of our knowledge, a new method for studying the motion of a particle trapped by optical tweezers; in this method the trapping beam itself is used as a confocal probe. By studying the response of the particle to periodic motion of the tweezers, we obtain information about the medium viscosity, particle properties,...

Surface Organization and Nanopatterning of Collagen by Dip Pen Nanolithography - Volume 8 Issue S02 - Donna L. Wilson, Raquel Martin, Mark Cronin-Golomb, Chad A. Mirkin, David L. Kaplan

The use of optical tweezers to measure micrometer-resolution velocity fields in fluid flow is demonstrated as an extension of a scanning confocal viscosity microscope. This demonstration is achieved by detection of the motion of an optically trapped microsphere in an oscillating laser trap. The technique is validated by comparison with an independe...

Confocal microscopy and optical tweezers were combined to develop a minimally invasive instrument capable of making hydrodynamic measurements more rapidly than is possible with other devices. This result leads to the possibility of making scanning images of the viscosity distribution of materials around bipolymer producing cells. An image of the vi...

Confocal microscopy and optical tweezers were combined to develop a minimally invasive instrument capable of making hydrodynamic measurements more rapidly than is possible with other devices. This result leads to the possibility of making scanning images of the viscosity distribution of materials around bipolymer producing cells. An image of the vi...

The techniques of confocal microscopy and optical tweezers have shown themselves to be powerful tools in biological and medical research. We combine these methods to develop a minimally invasive instrument that is capable of making hydrodynamic measurements more rapidly than is possible with other devices. This result leads to the possibility of ma...

In previous work, we used a confocal detection modification of a method to measure fluid viscosity by recording the response of a microsphere in a viscous medium under the action of rapidly oscillating photonic force. We showed that the viscosity of the fluid can be accurately and rapidly measured by detecting the phase lag of the motion. In this p...

Collagen is a key fibrous protein in biological systems, characterized by a complex structural hierarchy as well as the ability to self-assemble into liquid crystalline mesophases. The structural features of collagen influence cellular responses and material properties, with importance for a wide range of biomaterials and tissue architectures. The...

People with AD have deficient contrast sensitivity and impaired face discrimination. The authors presented photographs of unfamiliar faces of three different sizes to enhance the low, middle, or high facial frequency information (cycles per face). Patients with AD demonstrated normal discrimination of small faces only, indicating that impaired cont...

We report the numerical analysis and the fabrication of a reversed-ridge PLZT film waveguide. It is single-mode, has low transmission loss, and has large transverse cross-section suitable for efficient coupling to single-mode optical fibers. We used this structure to fabricate Mach-Zehnder (MZ) waveguide modulators. The field distribution in the ch...

Summary form only given. In the study of colloidal suspensions, polymer solutions and in cell and micro-biology it is often desirable to have a direct observation in real time of the changes in the local viscosity, which affect the dynamics of objects like colloidal particles, cells and organelles. For example, the cell's transport and diffusion of...

Erbium-doped Pb(Mg _1/3 Nb _2/3 )O ₃ –PbTiO ₃ (PMN–PT) thin films were grown on (10 1¯2) sapphire substrate with a purpose of developing an active optical material combining both the large electro-optic (EO) effect and lasing or amplification functions. Strong characteristic Er ³⁺ intra...

The experiments done in this grant can be broadly classified into two stages. The goal of both these stages was to demonstrate all-optical high-speed turbulence aberration correction through nonlinear optical phase conjugation. The first stage involved the development of a phase conjugate mirror (PCM) based on non-degenerate four-wave-mixiag (NDFWM...

The photorefractive effect in lead lanthanum zirconate titanate polycrystalline film, grown metallorganic chemical-liquid deposition, is demonstrated using degenerate four wave mixing. An applied external electric field induces the formation of a high diffraction efficiency photorefractive grating in a 15 μm thick film. A strongly field-dependent p...

The structural and quadratic electro-optic properties in lead magnesium niobate titanate thin films have been systematically studied as a function of the fraction x of lead titanate. (110)-oriented, pyrochlore-free PMN–PT films with PT contents around morphotropic phase boundary compositions, which have a propagation loss as low as 3 dB/cm and a hi...

© 1999 Optical Society of America

A cw degenerate phase conjugate resonator (PCR) with intracavity aero-optic turbulent flow is demonstrated using sodium vapor pumped with a low intensity cw laser. A turbulent helium jet at a high flow velocity of 250 m/s and forcing frequency of 18 kHz generated the spatio-temporal aberrations. The intracavity normalized peak-to-peak intensity flu...

We report the fabrication of new low-loss, large-cross-section single-mode PLZT (8.5/65/35) film reverse-ridge waveguides by depositing a PLZT film on an r-sapphire substrate with a patterned ITO spacer film. The single-mode profile and propagation losses were analyzed, and experimentally characterized at 0.633, 1.3, and 1.55 μm of light. ©1999 Joh...

We report the relatively low loss and large cross-section single mode PLZT film waveguide as well as its MZ type of an electro optic waveguide modulator. The reverse ridge waveguide was fabricated by first depositing an ITO thin film on an r-cut sapphire substrate. The ITO thickness was chosen to be in the range of submicrometer, as determined by a...

Highly (110)-oriented and (100) nearly epitaxial 0.7PMN-0.3PT thin films were deposited on (1012) sapphire and (100) LaAlO ₃ substrates, respectively, using a dip-coating method. Optical waveguide characterization and electro-optic effect measurements of the film on sapphire substrate were demonstrated. Low propagation loss of 4.1 dB/c...

Optical aberrations that are due to high-speed turbulence in the aero-optical regime are corrected with optical phase conjugation based on coherent population trapping in sodium vapor. Experimental measurements of an unheated, forced helium jet in air have demonstrated aberration correction by a factor of 7.8 at a forcing frequency of 18 kHz with a...

We observed optical gain as great as 30 with nearly distortion-free beam propagation in optically dense sodium vapor, using four-wave mixing. Moreover, 15-dB classical noise correlations were seen in the amplified probe and conjugate beams. To achieve this performance in such a strongly absorbing medium, one must suppress unwanted absorption and se...

We found stationary intensity profiles of photorefractive screening solitons in the presence of the diffusion processes. We show that these solitons are stable and in a certain range of parameters they propagate with negligible radiation losses along exactly parabolic trajectories. We studied the collision of screening solitons using numerical simu...

We have proposed homodyne and heterodyne techniques for imaging in a scattering medium. The first technique is based on the principle of the Doppler shift difference of the light which is scattered from an object vs light scattered by the surroundings. We showed that the principle of Doppler shift difference, and the principle of first arriving lig...

Antiparallel ferroelectric (180-deg) domains have been observed by high-resolution x-ray diffraction imaging in barium titanate and strontium barium niobate. This technique permits the imaging of domains in thick (1-mm) samples with high spatial resolution (1 µm). These domains are visible in both Laue and Bragg geometry but only in those diffracti...

Coherent population trapping can be used to achieve efficient optical phase conjugation in a double-(Lambda) system at pump intensities well below the saturation intensity of the optical transitions. Experimental evidence for this process in sodium vapor qualitatively verifies this prediction.

Summary form only given. Using coherent population trapping and nondegenerate four-wave mixing, we show that it is possible to simultaneously achieve high gain and diffraction-limited propagation of a weak probe, even though the sodium vapor is opaque to the probe in the absence of the pump beams. This distortion-free propagation is to be compared...

The double Raman (or double A system) has been the subject of much recent interest for applications such as lasing without inversion and precision laser frequency translation. We now show that coherent population trapping (CPT) in the double Raman system can be used to dramatically improve the performance of nonlinear optical materials that are bas...

An all-optical joint transform correlator featuring two operative correlation planes(ports) with complementary performance is presented. We present the theory of operation, derive the input–output characteristics, and demonstrate computer simulations and experimental results. The two-port joint transform correlator is based on simultaneous use of t...

Taking the crystal surface to be traction free, we calculate the lattice distortions and associated elasto-optic refractive-index changes induced by a photorefractive grating. The surface effects are significant and result in refractive-index changes near the surface that differ considerably from bulk values. Such surface effects should be of impor...

The spatial spectrum of angular phase matching for photorefractive devices that use orthogonally polarized reading and writing beams may be enhanced if the images are recorded at angles where the ordinary and extraordinary cross sections of the index ellipsoid have equal curvatures. Applications include holographic storage, phased-array radar proce...

A laser beam propagating in a photorefractive crystal generates a refractive-index profile that deflects the beam to one side. This nonlinear deflection can be balanced by total internal reflection at the crystal surface to produce self-induced photorefractive surface waves. Theoretical and experimental evidence for this effect is given.

In this work we presented a two port nonlinear joint transform correlator with two complimentary results. This correlator is based on a two port photorefractive limiting quadratic processor. In the limiting regime we demonstrated experimentally and by computer simulation, that the correlation operation is like a phase extraction correlator operatio...

Baseband demodulation, lock-in detection, noise reduction, compression/expansion nonlinearities, and correlation receivers are common subjects in communication theory. In this paper we use photorefractive materials to show how real-time holography can be used to implement these temporal electronic signal processing techniques as spatio-temporal opt...

The effectiveness of laser beam cleanup with photorefractive two-beam coupling is evaluated. We compare the measured effectiveness of the method with that of spatial filtering and find that the method works well for a highly aberrated beam approximately 700 times diffraction limited, whereas for moderately aberrated beams the effectiveness of the m...