We propose a method to measure the mode coefficient in a few-mode fiber with OAM modes. In this method, the eigenmodes are calculated through the optical fiber parameters, including LP modes and orbital angular momentum (OAM) modes. Using a single spatial light modulator (SLM) to load multi-channel computer-generated hologram (CGH), multiple matched filters can be generated at the same time to realize the real-time and accurate measurement of each mode coefficient (mode content and relative phase) and reconstruct the optical field. We validate the method on multimode beams, and the accuracy of mode coefficients measurement is up to 99%. It can be used as adaptive control coefficient to provide solutions for the expansion of photon lantern and other technologies.
Photonic lanterns can control beam modes by tuning phase, amplitude and polarization of multiple beam inputs, providing new methods to overcome mode instability in high-power large-mode area fiber lasers. The initial amplitude input of photonic lanterns are usually preset to be equal or random. The beam mode is then adaptively controlled by evaluating the beam output profile. This method can easily realize stable light output, but it sometimes runs into local optimum solutions. In this work, we propose a novel method to preset the initial amplitudes to realize better beam mode control. Based on the waveguide characteristics of the photonic lantern structure, we inversely work out the initial amplitude requirement of the input channels for controlling a certain mode using its transmission matrix. Taking 3×1 photonic lantern as an example, our simulation results show that this method can realize any mode control of LP01, LP11e, LP11o with their mode power ratios all above 99%, better than those preset methods to be equal or random. Our simulation method can be utilized in beam control experiments to achieve better beam control in photonic lantern-based fiber lasers
Photonic lanterns are a kind of low loss optical waveguide device which interfaces single multimode waveguides and multiple waveguides that support fewer modes. This paper focused on the fabrication process and the testing requirement of the performance of photonic lanterns. A method for evaluating the performance of a photonic lantern device using digital holographic grating correlation filtering method was proposed. The principle of mode decomposition and the layout of the experimental device were introduced. The real-time measurement of the mode compositions of the 3×1 photonic lantern was carried out. The correlation coefficient was used to evaluate the accuracy of the model measurement. The results showed that the correlation degree of the method was more than 97 %, which could be used to accurately evaluate the quality of the photonic lantern device.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
INSTITUTIONAL Select your institution to access the SPIE Digital Library.
PERSONAL Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.