( ( A laser ) ( ( is ( one ( of ( ( the ( few devices ) ) ( which ( ( generates light ) ( with ( only ( one wavelength ) ) ) ) ) ) ) ) ) . ) )
(ROOT (S (NP (DT A) (NN laser)) (VP (VBZ is) (NP (NP (CD one)) (PP (IN of) (NP (NP (DT the) (JJ few) (NNS devices)) (SBAR (WHNP (WDT which)) (S (VP (VBZ generates) (NP (NN light)) (PP (IN with) (NP (RB only) (CD one) (NN wavelength)))))))))) (. .)))
A laser is one of the few devices which generates light with only one wavelength.
(ROOT (S (NP (PRP You)) (VP (VBP call) (NP (NP (DT a) (NN device)) (SBAR (WHNP (WDT that)) (S (VP (VBZ produces) (NP (NP (DT a) (ADJP (RB very) (VBN focused)) (NN beam)) (PP (IN of) (NP (NP (JJ visible) (NN light)) (PP (IN of) (NP (NP (RB just) (CD one) (NN wavelength)) (CC and) (JJ color) (NP (DT a) (NN laser)))))))))))) (. .)))