Vertical cavity surface emitting laser comprising - a first reflector , - a second reflector comprising a layer stack of semiconductor or isolating layers, - an active region arranged between the first and second reflectors, and - an additional layer on top of the layer stack at the light output side, said additional layer forming an output interface of the laser, - wherein the refractive index of the additional layer is smaller than the smallest refractive index of the refractive indices of said layer stack, characterized by that the thickness of the additional layer is chosen such that a design parameter H(f r ) is in the range between 2.5 and 3.2 dB, and wherein the design parameter H(f r ) is determined by - applying a voltage that generates a predetermined bias current and a small sinusoidal current signal through the laser, - sweeping the frequency of the sinusoidal signal in a given frequency range, - measuring the small signal response of the radiation that leaves the laser at the output interface, - fitting the measured small signal response to the following transmission function H(f): H f = A ⋅ f R 2 f R 2 − f 2 + i γ 2 π f ⋅ 1 1 + i f f P and determining the parameters f R , γ , A and f P , wherein f R describes a relaxation resonance frequency, γ the damping parameter, A an offset and f R the 3 dB frequency of the laser's parasitics, and - calculating the design parameter H(f R ) by calculating the value of the transmission function H(f) at the relaxation resonance frequency f R based on the parameters that were determined as explained above. - a first reflector , - a second reflector comprising a layer stack of semiconductor or isolating layers, - an active region arranged between the first and second reflectors, and - an additional layer on top of the layer stack at the light output side, said additional layer forming an output interface of the laser, - wherein the refractive index of the additional layer is smaller than the smallest refractive index of the refractive indices of said layer stack, characterized by that the thickness of the additional layer is chosen such that a design parameter H(f r ) is in the range between 2.5 and 3.2 dB, and wherein the design parameter H(f r ) is determined by - applying a voltage that generates a predetermined bias current and a small sinusoidal current signal through the laser, - sweeping the frequency of the sinusoidal signal in a given frequency range, - measuring the small signal response of the radiation that leaves the laser at the output interface, - fitting the measured small signal response to the following transmission function H(f): H f = A ⋅ f R 2 f R 2 − f 2 + i γ 2 π f ⋅ 1 1 + i f f P and determining the parameters f R , γ , A and f P , wherein f R describes a relaxation resonance frequency, γ the damping parameter, A an offset and f R the 3 dB frequency of the laser's parasitics, and - calculating the design parameter H(f R ) by calculating the value of the transmission function H(f) at the relaxation resonance frequency f R based on the parameters that were determined as explained above. - applying a voltage that generates a predetermined bias current and a small sinusoidal current signal through the laser, - sweeping the frequency of the sinusoidal signal in a given frequency range, - measuring the small signal response of the radiation that leaves the laser at the output interface, - fitting the measured small signal response to the following transmission function H(f): H f = A ⋅ f R 2 f R 2 − f 2 + i γ 2 π f ⋅ 1 1 + i f f P and determining the parameters f R , γ , A and f P , wherein f R describes a relaxation resonance frequency, γ the damping parameter, A an offset and f R the 3 dB frequency of the laser's parasitics, and - calculating the design parameter H(f R ) by calculating the value of the transmission function H(f) at the relaxation resonance frequency f R based on the parameters that were determined as explained above. <EOS>