Patents by Inventor Rajeev J. Ram

Rajeev J. Ram has filed for patents to protect the following inventions. This listing includes patent applications that are pending as well as patents that have already been granted by the United States Patent and Trademark Office (USPTO).

  • Publication number: 20190195688
    Abstract: In swept source Raman (SSR) spectroscopy, a swept laser beam illuminates a sample, which inelastically scatters some of the incident light. This inelastically scattered light is shifted in wavelength by an amount called the Raman shift. The Raman-shifted light can be measured with a fixed spectrally selective filter and a detector. The Raman spectrum can be obtained by sweeping the wavelength of the excitation source and, therefore, the Raman shift. The resolution of the Raman spectrum is determined by the filter bandwidth and the frequency resolution of the swept source. An SSR spectrometer can be smaller, more sensitive, and less expensive than a conventional Raman spectrometer because it uses a tunable laser and a fixed filter instead of free-space propagation for spectral separation. Its sensitivity depends on the size of the collection optics. And it can use a nonlinearly swept laser beam thanks to a wavemeter that measures the beam's absolute wavelength during Raman spectrum acquisition.
    Type: Application
    Filed: December 21, 2018
    Publication date: June 27, 2019
    Inventors: Amir H. Atabaki, Rajeev J. RAM, William F. Herrington
  • Patent number: 9971226
    Abstract: An optoelectronic filter having at least one input and an output includes a modulator circuit having at least first and second inputs with a first one of the modulator circuit inputs adapted to couple to a respective one of the at least one input of the optoelectronic filter. The modulator circuit receives at least a first radio frequency (RF) signal having a first power level and a second RF signal having a second, different power level at the first one of the modulator circuit inputs and in response thereto generates a modulated signal at an output thereof. The first RF signal is suppressed relative to the second RF signal in the modulated signal. The optoelectronic filter additionally includes a light source adapted to couple to a second one of the modulator circuit inputs. A corresponding method is also provided.
    Type: Grant
    Filed: July 31, 2014
    Date of Patent: May 15, 2018
    Assignee: Massachusetts Institute of Technology
    Inventors: Paul W. Juodawlkis, William Loh, Rajeev J Ram, Siva Yegnanarayanan
  • Publication number: 20170346283
    Abstract: The systems and methods described herein are directed towards a microgrid having modular power management units to control and regulate power to maintain a stable energy environment and provide peer-to-peer electricity sharing within the microgrid. The microgrid includes a power source to generate power for the microgrid, a source power management unit coupled to the power source to receive the power, one or more load power management units coupled to the source power management unit to receive a portion of the power and a bi-directional communication system to couple the source power management unit to the one or more load power management units to control and allocate the power from the source power management unit to the one or more load power management units.
    Type: Application
    Filed: January 4, 2017
    Publication date: November 30, 2017
    Inventors: Wardah Inam, David J. Perreault, Rajeev J. Ram, Daniel DeWitt Strawser
  • Publication number: 20160170285
    Abstract: An optoelectronic filter having at least one input and an output includes a modulator circuit having at least first and second inputs with a first one of the modulator circuit inputs adapted to couple to a respective one of the at least one input of the optoelectronic filter. The modulator circuit receives at least a first radio frequency (RF) signal having a first power level and a second RF signal having a second, different power level at the first one of the modulator circuit inputs and in response thereto generates a modulated signal at an output thereof. The first RF signal is suppressed relative to the second RF signal in the modulated signal. The optoelectronic filter additionally includes a light source adapted to couple to a second one of the modulator circuit inputs. A corresponding method is also provided.
    Type: Application
    Filed: July 31, 2014
    Publication date: June 16, 2016
    Inventors: Paul W. Juodawlkis, William Loh, Rajeev J Ram, Siva Yegnanarayanan
  • Patent number: 8408786
    Abstract: In one aspect, the present invention provides techniques and apparatus for optical characterization of photonic devices and/or circuits. By way of example, the techniques can be used to identify damaged devices in photonic integrated circuits. In some embodiments, thermal imaging is employed as a diagnostic tool for characterizing the devices/circuits under investigation. For example, in one embodiment, integrated cascaded semiconductor amplifiers can be characterized using amplified spontaneous emission from one amplifier as a thermal modulation input to another amplifier. A thermoreflectance image of the second amplifier can reveal flaws, if present. Further, in some embodiments, thermal imaging in conjunction with a total energy model can be employed to characterize the elements of photonic circuits optically and/or to map the optical power distribution throughout the circuits.
    Type: Grant
    Filed: May 5, 2008
    Date of Patent: April 2, 2013
    Assignees: Massachusetts Institute of Technology (MIT), Mount Holyoke College
    Inventors: Janice A. Hudgings, Rajeev J. Ram, Maryam Farzaneh
  • Publication number: 20090245322
    Abstract: In one aspect, the present invention provides techniques and apparatus for optical characterization of photonic devices and/or circuits. By way of example, the techniques can be used to identify damaged devices in photonic integrated circuits. In some embodiments, thermal imaging is employed as a diagnostic tool for characterizing the devices/circuits under investigation. For example, in one embodiment, integrated cascaded semiconductor amplifiers can be characterized using amplified spontaneous emission from one amplifier as a thermal modulation input to another amplifier. A thermoreflectance image of the second amplifier can reveal flaws, if present. Further, in some embodiments, thermal imaging in conjunction with a total energy model can be employed to characterize the elements of photonic circuits optically and/or to map the optical power distribution throughout the circuits.
    Type: Application
    Filed: May 5, 2008
    Publication date: October 1, 2009
    Applicants: MASSACHUSETTS INSTITUTE OF TECHNOLOGY (MIT), MOUNT HOLYOKE COLLEGE
    Inventors: Janice A. Hudgings, Rajeev J. Ram, Maryam Farzaneh
  • Patent number: 7429735
    Abstract: The invention is directed to systems and methods of digital signal processing and in particular to systems and methods for measurements of thermoreflectance signals, even when they are smaller than the code width of a digital detector used for detection. For example, in some embodiments, the number of measurements done is selected to be sufficiently large so as to obtain an uncertainty less than the code width of the detector. This allows for obtaining images having an enhanced temperature resolution. The invention is also directed to methods for predicting the uncertainty in measurement of the signal based on one or more noise variables associated with the detection process and the number of measurement iterations.
    Type: Grant
    Filed: March 15, 2006
    Date of Patent: September 30, 2008
    Assignees: Mass Institute of Technology (MIT), Mount Holyoke College
    Inventors: Dietrich Lueerssen, Rajeev J. Ram, Janice A. Hudgings, Peter M. Mayer
  • Patent number: 7249881
    Abstract: A method and apparatus for performing characterization of devices is presented. The characteristic of the device are determined by obtaining a first temperature measurement in a first location of a device, obtaining a second temperature measurement, computing the difference between the temperature measurements and, using the temperatures and/or the temperature difference, a characteristic of the device is determined.
    Type: Grant
    Filed: April 29, 2005
    Date of Patent: July 31, 2007
    Assignee: Massachusetts Institute of Technology
    Inventors: Kevin P. Pipe, Rajeev J. Ram
  • Patent number: 7130494
    Abstract: A magneto-optical device includes a waveguide structure that has at least one cladding region and core region. The cladding region and core region comprise semiconductor alloy materials. Either the at least one cladding region or the core region is doped with ferromagnetic materials so as to increase the magneto-optical activity of the device.
    Type: Grant
    Filed: December 30, 2003
    Date of Patent: October 31, 2006
    Assignee: Massachusetts Institute of Technology
    Inventors: Rajeev J. Ram, Tauhid Zaman, Xiaoyun Guo
  • Patent number: 6921195
    Abstract: A method and apparatus for performing characterization of devices is presented. The characteristic of the device are determined by obtaining a first temperature measurement in a first location of a device, obtaining a second temperature measurement, computing the difference between the temperature measurements and, using the temperatures and/or the temperature difference, a characteristic of the device is determined.
    Type: Grant
    Filed: February 12, 2003
    Date of Patent: July 26, 2005
    Assignee: Massachusetts Institute of Technology
    Inventors: Kevin P. Pipe, Rajeev J. Ram
  • Patent number: 6834134
    Abstract: A method and apparatus are provided for generating short (e.g., picosecond) pulses using a 2 section 1553 nm DBR laser without gain switching nor external modulation. The center wavelength of the DBR section is modulated at 0.5 GHz to generate a constant amplitude frequency modulated optical wave Large group velocity dispersion is then applied with a chirped fiber Bragg grating to convert the FM signal to a pulse stream.
    Type: Grant
    Filed: March 23, 2001
    Date of Patent: December 21, 2004
    Assignee: 3M Innovative Properties Company
    Inventors: James F. Brennan, III, Patrick C. Chou, Harry L. T. Lee, Rajeev J. Ram, Hermann A. Haus, Erich P. Ippen
  • Publication number: 20040223719
    Abstract: A magneto-optical device includes a waveguide structure that has at least one cladding region and core region. The cladding region and core region comprise semiconductor alloy materials. Either the at least one cladding region or the core region is doped with ferromagnetic materials so as to increase the magneto-optical activity of the device.
    Type: Application
    Filed: December 30, 2003
    Publication date: November 11, 2004
    Inventors: Rajeev J. Ram, Tauhid Zaman, Xiaoyun Guo
  • Publication number: 20040077075
    Abstract: The present invention provides a variety of microscale bioreactors (microfermentors) and microscale bioreactor arrays for use in culturing cells. The microfermentors include a vessel for culturing cells and means for providing oxygen to the interior of the vessel at a concentration sufficient to support cell growth, e.g., growth of bacterial cells. Depending on the embodiment, the microfermentor vessel may have various interior volumes less than approximately 1 ml. The microfermentors may include an aeration membrane and optionally a variety of sensing devices. The invention further provides a chamber to contain the microfermentors and microfermentor arrays and to provide environmental control. Certain of the microfermentors include a second chamber that may be used, e.g., to provide oxygen, nutrients, pH control, etc., to the culture vessel and/or to remove metabolites, etc. Various methods of using the microfermentors, e.g., to select optimum cell strains or bioprocess parameters are provided.
    Type: Application
    Filed: May 1, 2003
    Publication date: April 22, 2004
    Applicant: Massachusetts Institute of Technology
    Inventors: Klavs F. Jensen, Paul Laibinis, Rajeev J. Ram, Anthony J. Sinskey, Nicolas Szita, Andrea Zanzotto, Martin A. Schmidt
  • Publication number: 20030152132
    Abstract: A method and apparatus for performing characterization of devices is presented. The characteristic of the device are determined by obtaining a first temperature measurement in a first location of a device, obtaining a second temperature measurement, computing the difference between the temperature measurements and, using the temperatures and/or the temperature difference, a characteristic of the device is determined.
    Type: Application
    Filed: February 12, 2003
    Publication date: August 14, 2003
    Inventors: Kevin P. Pipe, Rajeev J. Ram
  • Patent number: 6587492
    Abstract: A bipolar cascade-ARROW laser includes a plurality of core regions, at least one spacer disposed between each the plurality of core regions with each of the at least one spacers provided from a material having an index of refraction which is higher than an index of refraction of a material from which the core regions are provided. The bipolar cascade-ARROW laser further includes an anti-reflector disposed against each of the outermost ones of the core regions and at least one quantum well disposed in each of the plurality of core regions.
    Type: Grant
    Filed: March 1, 2001
    Date of Patent: July 1, 2003
    Assignee: Massachusetts Institute of Technology
    Inventors: Steven G. Patterson, Rajeev J. Ram
  • Patent number: 6426831
    Abstract: A wavelength division multiplexing (WDM) optical communication system includes an EIT based wavelength converter/switch. EIT, i.e., electromagnetically induced transparency, refers to the elimination of resonant absorption on an otherwise optically allowed transition by the application of a coherent coupling light field. In one embodiment, the EIT converter provides a 1×1 converter for converting a data stream from a first wavelength to a second wavelength. A constant wave probe field and a coherent coupling field, which has a state corresponding to data stream, are applied to the EIT medium. The converter can convert the data stream from a wavelength corresponding to the coupling field to the wavelength of the probe field. In a further embodiment, additional pairs of probe and coupling fields are applied to the EIT medium to provide an N×N converter.
    Type: Grant
    Filed: April 20, 2000
    Date of Patent: July 30, 2002
    Assignee: Massachusetts Institute of Technology
    Inventors: Holger Schmidt, Rajeev J. Ram
  • Publication number: 20010043628
    Abstract: A bipolar cascade-ARROW laser includes a plurality of core regions, at least one spacer disposed between each the plurality of core regions with each of the at least one spacers provided from a material having an index of refraction which is higher than an index of refraction of a material from which the core regions are provided. The bipolar cascade-ARROW laser further includes an anti-reflector disposed against each of the outermost ones of the core regions and at least one quantum well disposed in each of the plurality of core regions.
    Type: Application
    Filed: March 1, 2001
    Publication date: November 22, 2001
    Inventors: Steven G. Patterson, Rajeev J. Ram
  • Publication number: 20010036332
    Abstract: A method and apparatus are provided for generating short (e.g., picosecond) pulses using a 2 section 1553 nm DBR laser without gain switching nor external modulation. The center wavelength of the DBR section is modulated at 0.5 GHz to generate a constant amplitude frequency modulated optical wave Large group velocity dispersion is then applied with a chirped fiber Bragg grating to convert the FM signal to a pulse stream.
    Type: Application
    Filed: March 23, 2001
    Publication date: November 1, 2001
    Applicant: 3M Innovative Properties Company
    Inventors: James F. Brennan, Patrick C. Chou, Harry L.T. Lee, Rajeev J. Ram, Hermann A. Haus, Erich P. Ippen