Transforming a green laser pointer in a self-mixing interferometer capable of submicrometer vibration sensing.

We show that, by adding a photodiode and a plain glass beam splitter to a commercial green laser pointer, we can obtain a very sensitive self-mixing interferometer capable of detecting minute vibrations down to submicrometer amplitude, typically ≈13 resolution, or make displacement measurements with half-wavelength (/2=266) count increments.

Native signal self-mix interferometer has less than 1 nm noise equivalent displacement.

We demonstrate that the native configuration of a self-mixing interferometer attains a minimum detectable displacement of 0.72 nm or /1870 at the laser wavelength of 1310 nm, obtained by the bare laser diode package including a monitor photodiode, observed in the electrical domain by means of an oscilloscope and without any electronic processing of the signal.

"Quadrature detection for self-mixing interferometry" by Junfeng Wu and Fengfeng Shu: comment.

Some comments about the recently published Optics Letters paper "Quadrature detection for self-mixing interferometry," by Wu and Shu, Opt. Lett.43, 2154 (2018)OPLEDP0146-959210.

Numerical study of ultrashort-optical-feedback-enhanced photonic microwave generation using optically injected semiconductor lasers at period-one nonlinear dynamics.

This study numerically investigates the enhancement of photonic microwave generation using an optically injected semiconductor laser operating at period-one (P1) nonlinear dynamics through ultrashort optical feedback. For the purpose of practical applications where system miniaturization is generally preferred, a feedback delay time that is one to two orders of magnitude shorter than the relaxation resonance period of a typical laser is emphasized. Various dynamical states that are more complicated than the P1 dynamics can be excited under a number of ultrashort optical feedback conditions.

Systematic and random errors in self-mixing measurements: effect of the developing speckle statistics.

We consider the errors introduced by speckle pattern statistics of a diffusing target in the measurement of large displacements made with a self-mixing interferometer (SMI), with sub-λ resolution and a range up to meters. As the source on the target side, we assume a diffuser with randomly distributed roughness. Two cases are considered: (i) a developing randomness in z-height profile, with standard deviation σ(z), increasing from ≪λ to ≫λ and uncorrelated spatially (x,y), and (ii) a fully developed z-height randomness (σ(z)≫λ) but spatially correlated with various correlation sizes ρ(x,y).

Optical feedback stabilization of photonic microwave generation using period-one nonlinear dynamics of semiconductor lasers.

Effects of optical feedback on period-one nonlinear dynamics of an optically injected semiconductor laser are numerically investigated. The optical feedback can suppress the period-one dynamics and excite other more complex dynamics if the feedback level is high except for extremely short feedback delay times. Within the range of the period-one dynamics, however, the optical feedback can stabilize the period-one dynamics in such a manner that significant reduction of microwave linewidth and phase noise is achieved, up to more than two orders of magnitude.

Thickness measurement of transparent plates by a self-mixing interferometer.

We introduce a technique to measure transparent glass slab thickness. It employs a very simple setup combining two interferometers: a forward-going beam scheme and a self-mixing readout of the beam reflected back to the laser source. Interestingly, the difference of the two readouts provides a quantity related to thickness measurement, irrespective of refractive index.

Microconcentrators to recover fill-factor in image photodetectors with pixel on-board processing circuits.

We propose an array of non-imaging micro-concentrators as a mean to recover the loss of sensitivity due to area fill-factor. This is particularly important for those image photo detectors in which complex circuit functions are required and a substantial fraction of the pixel area is consumed, like e.g.

Self-mixing interferometer: analysis of the output signals.

This paper presents the calculation of amplitude and relative phase of signals at the three outputs available in a self-mixing interferometer, i.e. the front output on the target side, the back output on the rear of the chip, and, for diode laser, the junction voltage output.

Self-mixing differential vibrometer based on electronic channel subtraction.

An instrument for noncontact measurement of differential vibrations is developed, based on the self-mixing interferometer. As no reference arm is available in the self-mixing configuration, the differential mode is obtained by electronic subtraction of signals from two (nominally equal) vibrometer channels, taking advantage that channels are servo stabilized and thus insensitive to speckle and other sources of amplitude fluctuation. We show that electronic subtraction is nearly as effective as field superposition.