International comparison of eight semiconductor lasers stabilized on¹²⁷I₂at   = 633 nm

Abstract

An international comparison of eight I -stabilized semiconductor laser systems (DLs) has been carried out. Five of the DLs were extended-cavity lasers (ECLs) using extra-cavity saturation spectroscopy; another was a microlens-mounted diode modified to have weak optical feedback, stabilized using the same technique; the seventh ECL was stabilized using frequency-modulated spectroscopy. The final DL was a simple laser diode at 635 nm locked with a digital system on a linear absorption of iodine. The P(33) 6-3 transition of iodine was first used to compare the first seven DLs with a He-Ne laser stabilized on the R(127) 11-5 transition of iodine. The relative frequency stability of these lasers was between 5 parts in and 7 parts in for a sampling time of 1 s, with the best results less than 2 parts in over 1000 s. The frequency repeatability measured during one week was of the order of a few tens of kilohertz. This large fluctuation was caused by poor adjustment of the electronic offset of two of the lasers. For the well-corrected lasers, the repeatability was within a few kilohertz. A study of stabilization on the strong absorption group of transitions R(60) 8-4, R(125) 9-4 and P(54) 8-4, located about -12 GHz from the R(127) 11-5 transition, was also carried out. For the first time, a short-term frequency stability better than that of the classical He-Ne laser around 633 nm has been achieved with a relative frequency stability of 4 parts in for 1 s.

AFM nanometrology interferometric system with the compensation of angle errors

“…They were based on an extended-cavity configuration with a wavelength selective element replacing one of the cavity mirrors. They have proven that achievement of stable single-frequency operation is possible and their performance is good enough even for subdoppler spectroscopy and stabilization with relative frequency stability down to 10 -11 , see 14 . This is equal to the He-Ne laser, and more the technique offers large wavelength tuneability which can be of certain significance in special interferometric techniques 13,15 .…”

Multi-Wavelength Interferometry for Length Measurements Using Diode Lasers

“…The output intensity of a two beam interferometer is given in (2). The argument of the cosine function is the phase Φ of the interferometer signal and can be written as in (3). If the interferometer is operated with two optical wavelengths λ 1 and λ 2 the difference ∆Φ synth between the phases is given by nL nL…”

“…More sophisticated methods like stabilising the laser on an external cavity or onto atomic or molecular absorption lines, e.g. rubidium, potassium, or iodine, improves the stability by orders of magnitude (< 10 -9 ) [2], [3]. This paper gives an overview of three different applications of multi-wavelength interferometry which are well established at PTB: precision measurement of absolute distances (Chap.…”

Laser source for dimensional metrology: investigation of an iodine stabilized system based on narrow linewidth 633 nm DBR diode

“…This arrangement enabled narrowing the spectral width of the emission line down to tens of kHz while preserving the large tuning range. For example, an iodine stabilized ECL laser at 632.9 nm (vacuum wavelength) with approximately ten times better relative stability than iodine stabilized He-Ne laser has been reported [5]. Unfortunately, the mechanical construction of the external resonator and a short lifetime of the laser diode with an anti-reflective coating on the output facet render the ECL systems difficult to operate reliably on a long term scale.…”