Cascade Microtech, Inc.

Tektronix, Inc.

Apeldyn Corporation

Other

Scott H Rumbaugh

Leonard A Hayden

Mike Andrews

Philip J Bos

Michael D Jones

Andrew C Davidson

Friedrich Scheu

R Thomas Hawkins, Ii

An accessible optical path to a lower surface of a heatable device under test is provided by a thermal optical chuck comprising a transparent resistor deposited on transparent plate arranged to supporting the device in a probe station.

Thermal optical chuck

A direct current and a modulation signal are simultaneously applied to contact pads on a device under test, such as a laser diode, with a probe that reduces signal distortion and power dissipation by transmitting a modulated signal through an impedance matching resistor and transmitting of a direct current over a second signal path that avoids the impedance matching resistor.

Probe for combined signals

A direct current and a modulation signal are simultaneously applied to contact pads on a device under test, such as a laser diode. A probe and method of probing reduces signal distortion and power dissipation by transmitting a modulated signal to the device-under-test through an impedance matching resistor and transmitting of a direct current to the device-under-test over a second signal path that avoids the impedance matching resistor.

A direct current and a modulation signal are simultaneously applied to contact pads on a wafer to test certain devices, such as a laser diode. A probe, probing system, and method of probing reduces signal distortion and power dissipation by transmitting a modulated signal to the device-under-test through an impedance matching resistor and transmitting of a direct current to the device-under-test over a signal path that avoids the impedance matching resistor.

A cavity thickness compensated etalon filter. A tuning medium is placed in a Fabry-Perot etalon cavity. The index of refraction of the tuning medium varies as a function of voltage applied across the medium. The etalon is formed of two generally flat substrates disposed substantially parallel to one another. Each substrate has a layer of conductive material within the cavity adjacent the substrate. Each substrate also has a layer of reflective material within the cavity adjacent the substrate. At least one layer of reflective material is only partially reflective so as to enable light to pass into and out of the cavity. Liquid crystal material may be used as a tuning medium in the cavity. In the case of liquid crystal material, the etalon also comprises an alignment layer disposed within the cavity adjacent each substrate to pre-order the liquid crystal material. Means are provided for selectively varying the profile of the voltage across the tuning medium so as to compensate for variation in flatness and separation of the etalon substrates. Means are also provided to the render the filter polarization insensitive.

Cavity thickness compensated etalon filter

A fixture for angularly aligning an optical device. A monolithic structure is provided having a first adjustment member for holding an optical device and tilting the device in one direction, a second adjustment member attached to the first adjustment member for tilting the optical device in a direction orthogonal to the direction of tilt provided by the first adjustment member, and a base for holding the first and second adjustment members. The first adjustment member is attached to the second adjustment member by a flexible connection having a tilt axis in a first lateral direction and the second adjustment member is attached to the base by a connection having a tilt axis in a lateral direction orthogonal to the lateral direction of the first connection. Tilting of the first adjustment member with respect to the second adjustment member is accomplished by squeezing the first adjustment member toward the second adjustment member near the edges thereof or by pulling the first adjustment member away from the second adjustment member near the edges thereof. Tilting of the second adjustment member with respect to the base is accomplished in a similar manner. Preferably, the first and second adjustment members and the base are formed by cutting lateral slots partially through a cylindrical, monolithic member, the remaining portion of the monolithic member forming the flexible connection.

Fixture for angularly aligning an optical device

A fast response liquid crystal optical retarder system. A liquid crystal retarder system employs one or more liquid crystal cells and corresponding drive circuits. The drive circuits provide to the cell a rectangular wave ac voltage signal whose RMS voltage is controlled. To switch from one retardance to another, the voltage is increased or decreased beyond the voltage corresponding to the target retardance and then, prior to or when the target retardance is reached, the applied voltage is switched to the voltage corresponding to the target retardance. One or more pairs of liquid crystal cells provided sequentially along the path of light propagation and with their eigen-axis orthogonal to one another to increase or decrease the total retardance rapidly. The retarder system is incorporated in a polarization control system and in a fiber-optic link.

Liquid crystal cell retarder with driving beyond retardance value and

A method for on-wafer testing of microwave devices, such as photodiodes, including a biasing method applicable when the device has a lower end connected to the ground plane of the wafer. Elements having a diode-like characteristic, such as photodiodes, are arranged side-by-side with the device, each preferably being of like geometry with the device, and each having an end connected to the ground plane. A first voltage is applied between the ground conductors of the probe and the ground plane of the wafer to place each element in forward-biased condition thereby creating a return path for the lower end of the device to the ground conductors located on the upper side of the wafer. The method further includes a calibration method for accurate measurements of photodetectors particularly when they are biased as described above, including measuring a performance parameter, such as responsivity, that characterizes the optical performance of the photodetector, measuring a network parameter, such as a reflection coefficient, that characterizes the electrical performance of the photodetector, and determining an adjusted value for the performance parameter based on the network parameter in which the reference plane of the measured performance parameter has been shifted so as to better characterize the intrinsic response of the photodetector without interference by the surrounding measurement environment. Specific steps for removing probe effects and return path diode effects are described.

Method for measuring the electrical and optical performance of on-wafer

A fiber optic wafer probe, for use in measuring the parameters of photodetectors and other optoelectronic test devices at the wafer level, has a probe body along which an optical fiber extends to protrude from a tip of the probe body. The probe body loosely guides the optical fiber so that at least a significant portion of the length of the optical fiber is movable longitudinally with respect to the tip and probe body. This provides protection against excessive contact force between the fiber and the test device by enabling the optical fiber to buckle longitudinally in response to longitudinal overtravel of the fiber toward the test device. The probe body is of elongate shape with a probe tip at one end and a connector at the other end for detachably connecting the optical fiber to the probe body. The probe body length between the tip and connector is preferably substantially at least four inches to minimize undesirable multimode light transmission effects in a manner consistent with providing a replaceable fiber. The fiber is loosely guided through a bend along the probe body, which aids in minimizing the multimode effects.

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Lake Oswego, OR, United States of America

Scott H Rumbaugh