We are developing a stable and precise spectrograph for the Large Binocular Telescope (LBT) named "iLocater." The instrument comprises three principal components: a cross-dispersed echelle spectrograph that operates in the YJ-bands (0.97-1.30 µm), a fiber-injection acquisition camera system, and a wavelength calibration unit. iLocater will deliver high spectral resolution (R~150,000-240,000) measurements that permit novel studies of stellar and substellar objects in the solar neighborhood including extrasolar planets. Unlike previous planet-finding instruments, which are seeing-limited, iLocater operates at the diffraction limit and uses single mode fibers to eliminate the effects of modal noise entirely. By receiving starlight from two 8.4m diameter telescopes that each use "extreme" adaptive optics (AO), iLocater shows promise to overcome the limitations that prevent existing instruments from generating sub-meter-per-second radial velocity (RV) precision. Although optimized for the characterization of low-mass planets using the Doppler technique, iLocater will also advance areas of research that involve crowded fields, line-blanketing, and weak absorption lines.

The concept of light recycling has been misunderstood by many who work in the industry as they believe it would violate the brightness principle. This paper first tries to dispel that myth by providing an intuitive interpretation of the brightness principle and hence showing that light recycling is not a violation of this principle. It then goes on to present some general design guidelines as to how and if light recycling can be used in a particular system to enhance its throughput. A highly efficient (with near 100% recycling efficiency) light recycling system and some experimental results are also presented at the end.

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