My PhD training was specifically orientated towards developing theoretical models to predict the optical performance of multi-mode fibers and validate the models with experimental evidence.
I am now the lead fiber scientist for DESI and during the R&D phase of the project I undertook a great deal of fundamental fiber testing which allowed us to establish requirements and specifications within the fiber system. This work also allowed me to develop new fiber connection system using fiber splicing that greatly improved fiber performance.
Recently, I have also been motivated to understand the fiber performance in the near and far field of two types of robotic positioners that were being considered for DESI: tilting spine mechanical simulators and eccentric axis (or θ−φ) positioners. The far field performance of the fiber is important since the instrument efficiency is adversely affected if light from the fibers enters the spectrograph at a faster focal ratio than the spectrograph can accept (f/3.57 in the DESI design). This degradation of the focal ratio of light is caused by light entering the fiber off axis (tiliting positioner) or bending, twisting, and stress of the fiber (eccentric axis) positioner. The stability of the near field intensity distribution of the fiber is important since this determines the spectrograph point spread function (PSF). If the PSF changes from the calibration to the science exposures, this will result in an extraction bias. For DESI, a particular concern is the distortions in the PSF due to movement of the fibers during re-pointing.
In addition to managing the fiber system for DESI I was able to contribute a large effort to the design of the spectrograph through my theoretical modelling of VPH (volume phase holographic) grating design and efficiency. The gratings that I designed have now been manufactured and I will perform optical testing over the forthcoming months that will result in the ability to complete a demonstrator spectrograph unit.
Aside from DESI I am also part of a small team developing a high resolution fiber-fed echelle spectrograph that will be used to to study Earth-size planets, including those identified already by the NASA Kepler Mission and those as-yet-undiscovered that reside around other stars near our Solar System. A major driver comes from the Kepler Mission that has identified over 1000 planet “candidates” having sizes smaller than twice that of Earth. Major integration involves feeding starlight from the telescope to the spectrograph via an unprecedented series of fiber optic components, including fibers of circular cross-section, octagonal cross-section, and a double-fiber scrambler, to produce a stable illumination of the spectrograph optics.
I am now the lead fiber scientist for DESI and during the R&D phase of the project I undertook a great deal of fundamental fiber testing which allowed us to establish requirements and specifications within the fiber system. This work also allowed me to develop new fiber connection system using fiber splicing that greatly improved fiber performance.
Recently, I have also been motivated to understand the fiber performance in the near and far field of two types of robotic positioners that were being considered for DESI: tilting spine mechanical simulators and eccentric axis (or θ−φ) positioners. The far field performance of the fiber is important since the instrument efficiency is adversely affected if light from the fibers enters the spectrograph at a faster focal ratio than the spectrograph can accept (f/3.57 in the DESI design). This degradation of the focal ratio of light is caused by light entering the fiber off axis (tiliting positioner) or bending, twisting, and stress of the fiber (eccentric axis) positioner. The stability of the near field intensity distribution of the fiber is important since this determines the spectrograph point spread function (PSF). If the PSF changes from the calibration to the science exposures, this will result in an extraction bias. For DESI, a particular concern is the distortions in the PSF due to movement of the fibers during re-pointing.
In addition to managing the fiber system for DESI I was able to contribute a large effort to the design of the spectrograph through my theoretical modelling of VPH (volume phase holographic) grating design and efficiency. The gratings that I designed have now been manufactured and I will perform optical testing over the forthcoming months that will result in the ability to complete a demonstrator spectrograph unit.
Aside from DESI I am also part of a small team developing a high resolution fiber-fed echelle spectrograph that will be used to to study Earth-size planets, including those identified already by the NASA Kepler Mission and those as-yet-undiscovered that reside around other stars near our Solar System. A major driver comes from the Kepler Mission that has identified over 1000 planet “candidates” having sizes smaller than twice that of Earth. Major integration involves feeding starlight from the telescope to the spectrograph via an unprecedented series of fiber optic components, including fibers of circular cross-section, octagonal cross-section, and a double-fiber scrambler, to produce a stable illumination of the spectrograph optics.