Continuously Tunable Orbital Angular Momentum Generation Using a Polarization-maintaining Fiber

We demonstrate the generation of orbital angular momentum (OAM) in a two-mode polarization-maintaining (PM) optical fiber. We combine two linearly polarized modes of PM fiber to generate linearly polarized optical vortex beams with OAM. The average OAM can be finely varied by changing the phase between modes. We have quantitatively measured the resulting OAM to vary between ±1ℏ role= presentation style= box-sizing: border-box; display: inline; font-size: 12.88px; line-height: normal; word-spacing: normal; overflow-wrap: normal; white-space: nowrap; float: none; direction: ltr; max-width: none; max-height: none; min-width: 0px; min-height: 0px; border: 0px; padding: 0px; margin: 0px; position: relative; \u3e±1ℏ±1ℏ per photon while varying the relative phase between the LP11e role= presentation style= box-sizing: border-box; display: inline; font-size: 12.88px; line-height: normal; word-spacing: normal; overflow-wrap: normal; white-space: nowrap; float: none; direction: ltr; max-width: none; max-height: none; min-width: 0px; min-height: 0px; border: 0px; padding: 0px; margin: 0px; position: relative; \u3eLP11LP11e- and LP11o role= presentation style= box-sizing: border-box; display: inline; font-size: 12.88px; line-height: normal; word-spacing: normal; overflow-wrap: normal; white-space: nowrap; float: none; direction: ltr; max-width: none; max-height: none; min-width: 0px; min-height: 0px; border: 0px; padding: 0px; margin: 0px; position: relative; \u3eLP11LP11o-like fiber modes. The modal purity is 97%

Simultaneous Control of Orbital Angular Momentum and Beam Profile in Two-mode Polarization-maintaining Fiber

We report simultaneous control of the orbital angular momentum (OAM) and beam profile of vortex beams generated in two-mode polarization-maintaining optical fiber. Two higher-order eigenmodes of the fiber are combined to form optical vortices. Reduced coherence between the fiber modes decreases the mode purity. Varying the coherence of the fiber modes changes the average OAM while maintaining a constant annular intensity profile. Additionally, a donut mode has been shown to be insensitive to bends and twists in the fiber

Tunable Higher-order Orbital Angular Momentum using Polarization-maintaining Fiber

For the first time, to the best of our knowledge, light with orbital angular momentum (OAM) of ±2ℏ role= presentation style= box-sizing: border-box; display: inline; font-size: 12.88px; line-height: normal; word-spacing: normal; overflow-wrap: normal; white-space: nowrap; float: none; direction: ltr; max-width: none; max-height: none; min-width: 0px; min-height: 0px; border: 0px; padding: 0px; margin: 0px; position: relative; \u3e±2ℏ±2ℏ per photon is produced using commercially available polarization-maintaining fiber with modal purity of 96%. Twist measurements demonstrate that the average orbital angular momentum can be continuously tuned between ±2ℏ role= presentation style= box-sizing: border-box; display: inline; font-size: 12.88px; line-height: normal; word-spacing: normal; overflow-wrap: normal; white-space: nowrap; float: none; direction: ltr; max-width: none; max-height: none; min-width: 0px; min-height: 0px; border: 0px; padding: 0px; margin: 0px; position: relative; \u3e±2ℏ±2ℏ. The authors consider beams of non-integer OAM, created using the presented method, as superpositions of integer OAM states

Quantitative Measurement of the Orbital Angular Momentum of Light with a Single, Stationary Lens

We show that the average orbital angular momentum (OAM) of twisted light can be measured simply and robustly with a single stationary cylindrical lens and a camera. Theoretical motivation is provided, along with self-consistent optical modeling and experimental results. In contrast to qualitative interference techniques for measuring OAM, we quantitatively measure non-integer average OAM in mode superpositions

Compact diode laser source for multiphoton biological imaging

We demonstrate a compact, pulsed diode laser source suitable for multiphoton microscopy of biological samples. The center wavelength is 976 nm, near the peak of the two-photon cross section of common fluorescent markers such as genetically encoded green and yellow fluorescent proteins. The laser repetition rate is electrically tunable between 66.67 kHz and 10 MHz, with 2.3 ps pulse duration and peak powers \u3e1 kW. The laser components are fiber-coupled and scalable to a compact package. We demonstrate \u3e600 μm depth penetration in brain tissue, limited by laser power