Erik Sanchez | Portland State University (original) (raw)

Papers by Erik Sanchez

We report the imaging of single-molecule fluorescence induced by two-photon excitation in ambient... more We report the imaging of single-molecule fluorescence induced by two-photon excitation in ambient conditions. Using an inverted fluorescence microscope, we obtained the two-photon images of different single fluorophores (Rhodamine B, Sulforhodamine 101, Coumarin 535 on poly-methyl methacrylate films) and biological membrane fragments by Faster scanning the sample with respect to a diffraction limited focus of a mode-locked Ti: sapphire laser beam. The signal to background ratio was as high as 50:1 and the full width at half maximum (250nm) of a single-molecule peak was significantly shorter than that for one photon excitation. With its high sensitivity and simplicity, the two-photon experiment offers a valuable approach for spectroscopic studies on individual immobilized molecules.

Quantum Electronics and Laser Science Conference, May 18, 1997

Review of Scientific Instruments, Mar 1, 2023

Spatial heterodyne spectroscopy for fast local magnetic field measurements of magnetized fusion p... more Spatial heterodyne spectroscopy for fast local magnetic field measurements of magnetized fusion plasmas Review of Scientific Instruments 94, 033504 (2023);

Physical review. E, 2021

While the majority of fusion energy research is focused on magnetic confinement, there have been ... more While the majority of fusion energy research is focused on magnetic confinement, there have been several alternative confinement methods aimed at the development of smaller and less expensive reactors. A number of these alternative reactors are based on a spherically convergent beam of recirculating ions and include designs such as inertial electrostatic confinement (IEC), multigrid IEC, and the periodically oscillating plasma sphere concept. Here, a fully time-dependent GPU-based Vlasov solver was developed in order to study these spherically convergent devices. This code solves the Vlasov equation for a spherically symmetric system using a finite-volume method with a modified flux to account for electrode transparency. The solver accounts for secondary electron emission, interactions between the charged particles, and collisional effects such as ionization and charge exchange. This code was used to investigate a system similar to the ion-injected device described by Hirsch (see [R...

Bulletin of the American Physical Society, 2012

ABSTRACT It is important to teach students concepts and experimental skills relating to modern re... more ABSTRACT It is important to teach students concepts and experimental skills relating to modern research being performed today. Experiments that help educate students about the latest research helps them get jobs and into the doors at many great academic institutions. PSU's Advanced Experimental Class for physics undergraduates offers many novel experiments to help the students accomplish this task. Labs involving Plasmonics, thin film deposition, scanning probe microscopy (SPM) and more will be discussed. In addition, a new NSF funded project involving the building of a Do-It-Yourself (DIY) SPM will be discussed.

The Journal of Physical Chemistry A, 1998

Review of Scientific Instruments, 2011

Physical Review Letters, 2003

Physical Review Letters, 1999

We present a new scheme for near-field fluorescence imaging using a metal tip illuminated with fe... more We present a new scheme for near-field fluorescence imaging using a metal tip illuminated with femtosecond laser pulses of proper polarization. The strongly enhanced electric field at the metal tip (ഠ15 nm end diameter) results in a localized excitation source for molecular fluorescence. Excitation of the sample via two-photon absorption provides good image contrast due to the quadratic intensity dependence. The spatial resolution is shown to be better than that of the conventional aperture technique. We used the technique to image fragments of photosynthetic membranes, as well as J-aggregates with spatial resolutions on the order of 20 nm. [S0031-9007(99)09142-5]

Journal of the Optical Society of America A, 2012

Reconstruction of an image (or shape or wavefront) from measurements of the derivatives of the im... more Reconstruction of an image (or shape or wavefront) from measurements of the derivatives of the image in two orthogonal directions is a common problem. We demonstrate how a particular reconstructor, commonly referred to as the Fried algorithm, can be used with megapixel derivative images to recover the original image. Large datasets are handled by breaking the derivative images into smaller tiles, applying the Fried algorithm and stitching the tiles back together. The performance of the algorithm is demonstrated using differential interference contrast microscopy on a known test object.

Microscopy and Microanalysis, 2011

Extended abstract of a paper presented at Microscopy and Microanalysis 2011 in Nashville, Tenness... more Extended abstract of a paper presented at Microscopy and Microanalysis 2011 in Nashville, Tennessee, USA, August 7–August 11, 2011.

Microscopy and Microanalysis, 2011

Extended abstract of a paper presented at Microscopy and Microanalysis 2011 in Nashville, Tenness... more Extended abstract of a paper presented at Microscopy and Microanalysis 2011 in Nashville, Tennessee, USA, August 7–August 11, 2011.

Applied Optics, 2010

We present the development of a versatile spectroscopic imaging tool to allow for imaging with si... more We present the development of a versatile spectroscopic imaging tool to allow for imaging with singlemolecule sensitivity and high spatial resolution. The microscope allows for near-field and subdiffractionlimited far-field imaging by integrating a shear-force microscope on top of a custom inverted microscope design. The instrument has the ability to image in ambient conditions with optical resolutions on the order of tens of nanometers in the near field. A single low-cost computer controls the microscope with a field programmable gate array data acquisition card. High spatial resolution imaging is achieved with an inexpensive CW multiphoton excitation source, using an apertureless probe and simplified optical pathways. The high-resolution, combined with high collection efficiency and single-molecule sensitive optical capabilities of the microscope, are demonstrated with a low-cost CW laser source as well as a mode-locked laser source.

Microscopy Today

Recent advances in nanotechnology and nanoscience are highly dependent on our newly acquired abil... more Recent advances in nanotechnology and nanoscience are highly dependent on our newly acquired ability to measure and manipulate individual structures on the nanoscale. A drawback of light microscopy is the fundamental limit of the attainable spatial resolution dictated by the laws of diffraction at about 250 nanometers. This diffraction limit arises from the fact that it is impossible to focus light to a spot smaller than half its wavelength. The challenge of breaking this limit has led to the development of near-field scanning optical microscopy (NSOM).

Microscopy and Microanalysis

Traditional light microscopy suffers from the diffraction limit, which limits the spatial resolut... more Traditional light microscopy suffers from the diffraction limit, which limits the spatial resolution to lambda/2. Near-field optical microscopes allow for imaging at resolutions lower than the diffraction limit. Using a combination of a hybrid atomic force microscope and an inverted optical microscope, resolutions below 20 nm have been demonstrated. The imaging probes for the AFM are specially shaped metal tips

We report the imaging of single-molecule fluorescence induced by two-photon excitation in ambient... more We report the imaging of single-molecule fluorescence induced by two-photon excitation in ambient conditions. Using an inverted fluorescence microscope, we obtained the two-photon images of different single fluorophores (Rhodamine B, Sulforhodamine 101, Coumarin 535 on poly-methyl methacrylate films) and biological membrane fragments by Faster scanning the sample with respect to a diffraction limited focus of a mode-locked Ti: sapphire laser beam. The signal to background ratio was as high as 50:1 and the full width at half maximum (250nm) of a single-molecule peak was significantly shorter than that for one photon excitation. With its high sensitivity and simplicity, the two-photon experiment offers a valuable approach for spectroscopic studies on individual immobilized molecules.

Quantum Electronics and Laser Science Conference, May 18, 1997

Review of Scientific Instruments, Mar 1, 2023

Spatial heterodyne spectroscopy for fast local magnetic field measurements of magnetized fusion p... more Spatial heterodyne spectroscopy for fast local magnetic field measurements of magnetized fusion plasmas Review of Scientific Instruments 94, 033504 (2023);

Physical review. E, 2021

While the majority of fusion energy research is focused on magnetic confinement, there have been ... more While the majority of fusion energy research is focused on magnetic confinement, there have been several alternative confinement methods aimed at the development of smaller and less expensive reactors. A number of these alternative reactors are based on a spherically convergent beam of recirculating ions and include designs such as inertial electrostatic confinement (IEC), multigrid IEC, and the periodically oscillating plasma sphere concept. Here, a fully time-dependent GPU-based Vlasov solver was developed in order to study these spherically convergent devices. This code solves the Vlasov equation for a spherically symmetric system using a finite-volume method with a modified flux to account for electrode transparency. The solver accounts for secondary electron emission, interactions between the charged particles, and collisional effects such as ionization and charge exchange. This code was used to investigate a system similar to the ion-injected device described by Hirsch (see [R...

Bulletin of the American Physical Society, 2012

ABSTRACT It is important to teach students concepts and experimental skills relating to modern re... more ABSTRACT It is important to teach students concepts and experimental skills relating to modern research being performed today. Experiments that help educate students about the latest research helps them get jobs and into the doors at many great academic institutions. PSU's Advanced Experimental Class for physics undergraduates offers many novel experiments to help the students accomplish this task. Labs involving Plasmonics, thin film deposition, scanning probe microscopy (SPM) and more will be discussed. In addition, a new NSF funded project involving the building of a Do-It-Yourself (DIY) SPM will be discussed.

The Journal of Physical Chemistry A, 1998

Review of Scientific Instruments, 2011

Physical Review Letters, 2003

Physical Review Letters, 1999

We present a new scheme for near-field fluorescence imaging using a metal tip illuminated with fe... more We present a new scheme for near-field fluorescence imaging using a metal tip illuminated with femtosecond laser pulses of proper polarization. The strongly enhanced electric field at the metal tip (ഠ15 nm end diameter) results in a localized excitation source for molecular fluorescence. Excitation of the sample via two-photon absorption provides good image contrast due to the quadratic intensity dependence. The spatial resolution is shown to be better than that of the conventional aperture technique. We used the technique to image fragments of photosynthetic membranes, as well as J-aggregates with spatial resolutions on the order of 20 nm. [S0031-9007(99)09142-5]

Journal of the Optical Society of America A, 2012

Reconstruction of an image (or shape or wavefront) from measurements of the derivatives of the im... more Reconstruction of an image (or shape or wavefront) from measurements of the derivatives of the image in two orthogonal directions is a common problem. We demonstrate how a particular reconstructor, commonly referred to as the Fried algorithm, can be used with megapixel derivative images to recover the original image. Large datasets are handled by breaking the derivative images into smaller tiles, applying the Fried algorithm and stitching the tiles back together. The performance of the algorithm is demonstrated using differential interference contrast microscopy on a known test object.

Microscopy and Microanalysis, 2011

Extended abstract of a paper presented at Microscopy and Microanalysis 2011 in Nashville, Tenness... more Extended abstract of a paper presented at Microscopy and Microanalysis 2011 in Nashville, Tennessee, USA, August 7–August 11, 2011.

Microscopy and Microanalysis, 2011

Extended abstract of a paper presented at Microscopy and Microanalysis 2011 in Nashville, Tenness... more Extended abstract of a paper presented at Microscopy and Microanalysis 2011 in Nashville, Tennessee, USA, August 7–August 11, 2011.

Applied Optics, 2010

We present the development of a versatile spectroscopic imaging tool to allow for imaging with si... more We present the development of a versatile spectroscopic imaging tool to allow for imaging with singlemolecule sensitivity and high spatial resolution. The microscope allows for near-field and subdiffractionlimited far-field imaging by integrating a shear-force microscope on top of a custom inverted microscope design. The instrument has the ability to image in ambient conditions with optical resolutions on the order of tens of nanometers in the near field. A single low-cost computer controls the microscope with a field programmable gate array data acquisition card. High spatial resolution imaging is achieved with an inexpensive CW multiphoton excitation source, using an apertureless probe and simplified optical pathways. The high-resolution, combined with high collection efficiency and single-molecule sensitive optical capabilities of the microscope, are demonstrated with a low-cost CW laser source as well as a mode-locked laser source.

Microscopy Today

Recent advances in nanotechnology and nanoscience are highly dependent on our newly acquired abil... more Recent advances in nanotechnology and nanoscience are highly dependent on our newly acquired ability to measure and manipulate individual structures on the nanoscale. A drawback of light microscopy is the fundamental limit of the attainable spatial resolution dictated by the laws of diffraction at about 250 nanometers. This diffraction limit arises from the fact that it is impossible to focus light to a spot smaller than half its wavelength. The challenge of breaking this limit has led to the development of near-field scanning optical microscopy (NSOM).

Microscopy and Microanalysis

Traditional light microscopy suffers from the diffraction limit, which limits the spatial resolut... more Traditional light microscopy suffers from the diffraction limit, which limits the spatial resolution to lambda/2. Near-field optical microscopes allow for imaging at resolutions lower than the diffraction limit. Using a combination of a hybrid atomic force microscope and an inverted optical microscope, resolutions below 20 nm have been demonstrated. The imaging probes for the AFM are specially shaped metal tips