Design of GRIN laser beam shaping system

Shealy, David L.; Chao, Shao-Hua

doi:10.1117/12.557436

Cited by 12 publications

(4 citation statements)

References 22 publications

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“…A photodiode directly coupled to a 9µm core diameter SMF was compared to a similar photodiode coupled to a GRIN lens. The beam shaping effect of GRIN lenses has been studied previously [9]. The simulated incident optical intensity profiles at 1550nm wavelength are shown in Fig.…”

Section: Device Descriptionmentioning

confidence: 99%

High-power handling, ultra-fast, GRIN lens-coupled photodetectors

2008

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The performance of microwave photonic systems can be improved by utilizing high power handling photodetectors. Operation at higher photocurrents enables larger output RF signals to be produced directly by the photodetector. This reduces the requirement of signal amplification by RF amplifiers, thereby simultaneously improving the dynamic range and the noise figure. In optical coherent systems, high power handling photodetectors enable operation at high local oscillator power levels to boost the coherent gain and the detection sensitivity. Thus, techniques to enhance the power handling capability of photodetectors are of interest for both free space and fiber based applications.Photodetector current saturates at high optical power levels due to space-charge screening effect. The saturation effect is maximized where the illumination intensity, and the resulting photocurrent density, is largest. In this work, we focus on optimizing the optical field profile incident on top-illuminated InGaAs photodiodes to minimize the peak photocurrent density. This was achieved by employing graded-index (GRIN) lens coupling to uniformly distribute the optical power across the diode cross-section.We demonstrate 5dB improvement in photodiode's power handling capability and linearity by employing GRIN lens coupling as compared to single mode fiber (SMF) coupling. Our GRIN lens-coupled photodetectors have achieved small-signal 1dB compression current of >50mA and 12.5dBm amplifier-free RF output. These devices also exhibit linear behavior for a peak-to-peak RF pulse output of >2.5V, at ~30ps pulse width. This constitutes a 100% improvement over SMF coupled devices. Further, the GRIN photodiodes demonstrate pulse broadening =0.65ps/mW, as compared to 2ps/mW for SMF devices.

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Section: Device Descriptionmentioning

confidence: 99%

High-power handling, ultra-fast, GRIN lens-coupled photodetectors

2008

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“…energy and OPL conditions. Similar methods are used for transforming an elliptical beam into a Fermi-Dirac output profile by using a two-mirror system [87] and to design gradient-index laser beam shapers [88].…”

Section: A Laser Beam Shaping Of Single-emitter Lasersmentioning

confidence: 99%

Laser-based displays: a review

2010

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After the invention of lasers, in the past 50 years progress made in laser-based display technology has been very promising, with commercial products awaiting release to the mass market. Compact laser systems, such as edge-emitting diodes, vertical-cavity surface-emitting lasers, and optically pumped semiconductor lasers, are suitable candidates for laser-based displays. Laser speckle is an important concern, as it degrades image quality. Typically, one or multiple speckle reduction techniques are employed in laser displays to reduce speckle contrast. Likewise, laser safety issues need to be carefully evaluated in designing laser displays under different usage scenarios. Laser beam shaping using refractive and diffractive components is an integral part of laser displays, and the requirements depend on the source specifications, modulation technique, and the scanning method being employed in the display. A variety of laser-based displays have been reported, and many products such as pico projectors and laser televisions are commercially available already.

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“…Second, note that in the process of propagation, the elliptical Gaussian beam will be deflected owing to the nonaligned lens axis and the laser light, which is difficult to compensate by beam shaping. [22][23][24][25] This deflection will directly affect the characteristics of the results, and the Gaussian distribution of the laser SW field will change. The resulting spatial dependence Gðx; y; zÞ of the laser intensity is given by Gðx; y; zÞ…”

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confidence: 99%

Nanofabrication of millimeter-level nanostructure via laser-focused atomic deposition

Zhang¹,

Yin²,

Zhao³

et al. 2018

Appl. Phys. Express

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We describe the fabrication of a large area of chromium nanogratings formed by laser focusing techniques. The focusing occurs in an elliptical laser standing-wave field, resulting in a line array covering an area of approximately 1.5 ' 1.5 mm 2 with a spacing of 212.78 nm. The experimental arrangement for laser focusing is described. Improvements in the technique and potential applications are also mentioned.

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Design of GRIN laser beam shaping system

Cited by 12 publications

References 22 publications

High-power handling, ultra-fast, GRIN lens-coupled photodetectors

High-power handling, ultra-fast, GRIN lens-coupled photodetectors

Laser-based displays: a review

Nanofabrication of millimeter-level nanostructure via laser-focused atomic deposition

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