A functional block diagram of the TPA test setup is shown in Figure B.1. Important components are called out specifically with white numbers inside of black circles. More information is provided about these components in Table B.1. In the block diagram, red lines indicate the optical path traveled by the beam as it exits the laser source. Where necessary, red triangles have been included in the diagram to indicate the direction of travel of the beam at specific locations along the optical path. The dark blue line originating from the focusing objective indicates the reflected light that is imaged by the near-infrared camera (number 8 in Figure B.1). The light blue lines connecting the computer (11) to the
stage controllers (15 and 16) and the stage controllers to the stages (12 and 13) represent electrical and data connections between these components.
Several components in the diagram are not called out with numbers. These are primarily mirrors used to guide the beam along the optical path (M1 through M7) and beam splitters used to direct the beam to the InGaAs photodiode that measures the pulse energy during testing and the near-infrared camera (BS1 and BS2). A small focusing lens can be found inside the black box (L1). The purpose of this lens is to maintain a known spot size on the photodiode’s InGaAs detector element. The importance of this will be discussed in Section B.3.
FigureB.1:AsimplifiedblockdiagramoftheTPAtestsetup.ThenumberedcomponentsaredescribedinTableB.1.
Table B.1: The names and descriptions of the components of the TPA test setup shown in Figure B.1.
TPA Test Setup Component List
Number Description
1 Laser Source
A TiS-pumped Optical Parametric Generator which pro- duces a 150 fs pulse (nominal) with a 1260 nm wavelength at a 1 kHz pulse rate.
2 Spatial Filter
A rail-mounted section of the optical path consisting of var- ious components (irises, lens, pinhole) used to direct, align, and shape the beam.
3 Periscope
Post-mounted mirrors intended to raise the optical height and change the direction of the beam. Mirrors are Melles Griot part number TLM2-1260-45P-1025.
4 Mounted Achromatic Half-Wave Plate
Provides continuous pulse energy adjustment. The primary means by which the user adjusts the incident laser pulse energy during testing. Part number AHWP05M-1600 from Thor Labs.
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Table B.1: (continued) TPA Test Setup Component List
Number Description
5 Polarizer
Adjusts the beam polarization following the Half-Wave plate. A means of controlling the incident pulse energy that is not intended to be adjusted during measurements. The polarizer crystal is Glan-Taylor (available via Thor Labs) part number GT10-C. The mount is Thor Labs PRM1Gl10 with lens tube part number SM1PM10.
6 InGaAs Photodiode
The primary means by which the pulse energy is measured during experiments. The photodiode peak current response has been calibrated to the incident laser pulse energy at the DUT location (see Section B.3). Part number ET-3020 from EOT, Inc.
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Table B.1: (continued) TPA Test Setup Component List
Number Description
7 Black Box
A light-tight box responsible for directing the beam to the focusing objective, InGaAs photodiode, and infrared cam- era. A focusing lens is included in front of the InGaAs photodiode to ensure that the entire beam is incident on the InGaAs detector. The focusing lens is Thor Labs N-BK7 Plano-Convex with a 1” diameter and a 1” focal length (part number LA1951). The beam splitters are Melles Griot part number FABS-1260-45P-PW-1006-UV.
8 Near IR Camera
A near-infrared camera whose purpose is to image the DUT and the laser spot of the focused 1260 nm beam.
9 Silicon Window
A thin, polished silicon window. The purpose of this com- ponent is to absorb visible light (and pass infrared light) back into the black box. This keeps stray visible light from interfering with the near-infrared camera image. Part num- ber is SI-W-25-1 from ISP Optics.
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Table B.1: (continued) TPA Test Setup Component List
Number Description
10 Broad Spectrum Light Source
Provides background illumination through the focusing ob- jective for imaging devices under test. It is a Model 2900 Tungsten Halogen Light Source manufactured by Illumina- tion Technologies.
11 Computer
A Windows-based PC that runs software for controlling the X, Y, and Z stages. Also interfaces with various pieces of measurement equipment for capturing and analyzing exper- imental data. Instrument connection software is Agilent Connection Expert. In-house software for automated data collection and analysis is written using MATLAB. It is dis- cussed in more detail in [87].
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Table B.1: (continued) TPA Test Setup Component List
Number Description
12, 15 Probe Station, XY-Stages and Controller
Modified probe station for mounting DUTs and probes (if needed). The probe station was manufactured by Creative Devices and modified in-house at Vanderbilt. The XY- stages are mounted beneath probe station platen to move the entire probe station surface. The XY-stages have a 0.1µm resolution. The stages were manufactured by Danaher, the motion controller and software were manufactured by Galil (model number 1826).
13, 16 Z-stage and Controller
Z-stage and controller manufactured by Newport. Controls the Z-location of the focused laser spot. Model number for stage motor is GTS30V. Model number for Z-stage con- troller is Newport ESP301. The Z-stage has a 0.1µm reso- lution. The focusing objective is mounted to the stage using a custom-milled metal bracket.
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Table B.1: (continued) TPA Test Setup Component List
Number Description
14 Focusing Objective
Focuses the incoming laser light to a small spot size. Two objectives are common on this setup, the Mitutoyo Plan Apo NIR 50X and the Mitutoyo Plan Apo NIR 100X. Of the two, the 100X version is the most commonly used for SEE ex- perimental work. Both are available from Edmund Optics.
17 Device Under Test
The DUT mounts to a custom-milled plate with a standard optical hole pattern (1/4”-20, 1” on center). A large hole in the center of the plate allows the beam to pass through the plate and onto the DUT. Alternatively, mounting holes are provided to accommodate the high-speed packages de- scribed in Chapter 3.