One embodiment provides an optical spectrometer. The optical spectrometer can include a lens-and-filter system configured to collect light scattered from a sample, a spot converter configured to convert a substantially circular beam outputted from the lens-and-filter system into a substantially rectangular beam, and a slit comprising a rectangular aperture to allow a predetermined portion of the substantially rectangular beam to enter the rectangular aperture while blocking noise. The slit can further include at least one microelectromechanical systems (MEMS)-based movable structure configured to adjust a width of the rectangular aperture.

One embodiment provides an optical spectrometer. The optical spectrometer can include a lens-and-filter system configured to collect light scattered from a sample, a spot converter configured to convert a substantially circular beam outputted from the lens-and-filter system into a substantially rectangular beam, and a slit comprising a rectangular aperture to allow a predetermined portion of the substantially rectangular beam to enter the rectangular aperture while blocking noise. The slit can further include at least one microelectromechanical systems (MEMS)-based movable structure configured to adjust a width of the rectangular aperture.

An example optical fiber signal mode conversion apparatus includes a non-single-mode optical fiber and a single-mode optical fiber. The single-mode optical fiber forms, with the non-single-mode optical fiber, a first coupling region and a second coupling region along a signal transmission direction in the non-single-mode optical fiber, where an effective refractive index of a fundamental mode signal of the single-mode optical fiber in the first coupling region is equal to an effective refractive index of a signal in a first mode, the signal in the first mode is coupled to a fundamental mode channel of the single-mode optical fiber, and an effective refractive index of the fundamental mode signal of the single-mode optical fiber in the second coupling region is equal to an effective refractive index of a signal in a second mode.

An example optical fiber signal mode conversion apparatus includes a non-single-mode optical fiber and a single-mode optical fiber. The single-mode optical fiber forms, with the non-single-mode optical fiber, a first coupling region and a second coupling region along a signal transmission direction in the non-single-mode optical fiber, where an effective refractive index of a fundamental mode signal of the single-mode optical fiber in the first coupling region is equal to an effective refractive index of a signal in a first mode, the signal in the first mode is coupled to a fundamental mode channel of the single-mode optical fiber, and an effective refractive index of the fundamental mode signal of the single-mode optical fiber in the second coupling region is equal to an effective refractive index of a signal in a second mode.

A photonic crystal optical phased array device has a dispersion engineered slow light waveguide region; a mode coupler region capable of optically coupling an input waveguide to the dispersion engineered slow light waveguide region; and optical antenna regions integrated within the dispersion engineered slow light waveguide region. The dispersion engineered slow light waveguide region has a substantially linear dispersion relation within a predetermined operational bandwidth of the optical phased array device. The optical antenna regions are formed by an alteration of a periodic structure of the photonic crystal and are capable of radiating light out from the dispersion engineered slow light waveguide region.

A photonic crystal optical phased array device has a dispersion engineered slow light waveguide region; a mode coupler region capable of optically coupling an input waveguide to the dispersion engineered slow light waveguide region; and optical antenna regions integrated within the dispersion engineered slow light waveguide region. The dispersion engineered slow light waveguide region has a substantially linear dispersion relation within a predetermined operational bandwidth of the optical phased array device. The optical antenna regions are formed by an alteration of a periodic structure of the photonic crystal and are capable of radiating light out from the dispersion engineered slow light waveguide region.

The present invention provides a method for converting the topological charge of an orbital angular momentum mode of light to an opposite topological charge by applying the light to a spool of optical fiber having a bend radius R and length L. The length of the fiber used to form the spool is defined by ½ the bend-induced 2π walk-off length L.sub.l,m.sup.b(2π). The length of the fiber L and the bend radius R of the spool may be adjusted to account for an ellipticity-induced 2π walk-off length L.sub.l,m.sup.3(2π). Using the proportionality rules, L.sub.l,m.sup.b(2π)∝R.sup.2l and L.sub.l,m.sup.3(2π)∝ε.sup.−l adjustments to account for ellipticity induced 2π walk-off length L.sub.l,m.sup.e(2π), or to account for a change in the bend radius ΔR of the spool can be easily determined.

The present invention provides a method for converting the topological charge of an orbital angular momentum mode of light to an opposite topological charge by applying the light to a spool of optical fiber having a bend radius R and length L. The length of the fiber used to form the spool is defined by ½ the bend-induced 2π walk-off length L.sub.l,m.sup.b(2π). The length of the fiber L and the bend radius R of the spool may be adjusted to account for an ellipticity-induced 2π walk-off length L.sub.l,m.sup.3(2π). Using the proportionality rules, L.sub.l,m.sup.b(2π)∝R.sup.2l and L.sub.l,m.sup.3(2π)∝ε.sup.−l adjustments to account for ellipticity induced 2π walk-off length L.sub.l,m.sup.e(2π), or to account for a change in the bend radius ΔR of the spool can be easily determined.

A first multimode optical fiber carries a mode division multiplexed (MDM) optical signal. The MDM optical signal is transmitted into a second multimode fiber from the first multimode optical fiber. The first and second multimode fibers are coupled via a fiber connector. The lateral offset between the two fibers at the connector is less than 2 μm.

A first multimode optical fiber carries a mode division multiplexed (MDM) optical signal. The MDM optical signal is transmitted into a second multimode fiber from the first multimode optical fiber. The first and second multimode fibers are coupled via a fiber connector. The lateral offset between the two fibers at the connector is less than 2 μm.