λ for [dl] has been used in Eskimo by Jenness ... ƛ for [tł] is an innovation formed from λ as ł from l.
It is also commonly used to represent this phoneme in several languages of the Caucasus. A barred lambda is used in transcribing Sahaptin, e.g., iƛúpna ‘he jumped’. It occurs there less frequently than its ejective counterpart, e.g., iƛ’úna ‘he guessed right (in the bone game)’.
In physics, it is used to represent a wavelength (λ) divided by 2π, i.e., the length taken up by one radian of the wave.