As has been noted the problem is not really launching the aircraft but recovering them. One possibility is to use a tail-sitter VTOL and if you do a Google image search for "Boeing an-1" you will find several images of designs for a such a system.
Of note is that these designs - and the operational aircraft carrying submarines - do not have a single pressure hull containing the hangar. Either an arrangement similar to the SSGN USS Halibut is used, where the hangar is composed of angled pressure hulls with the aircraft withdrawn through hatches at the rear end, or alternatively the aircraft are housed in fat vertical tubes, like the missiles on an SSBN. You could of course arrange these with multiple pressure hulls side-by-side.
The hull shape of such a submarine would be different from normal, as you would want to improve the stability on the surface - unless stabilisers were fitted (IIRC the Russian Typhoon class actually has bilge keels to improve surfaced motions). This, plus the larger external casing to wrap around all the pressure hulls, would increase the powering requirements.
This, plus all the extra structure - and not just more tubes, mind you, but complicated forged inserts and transitions and external stiffening to stop the hulls breaking off under shock - would increase the cost "somewhat". Which raises the question of "why?". On the plus side all the extra steel would help to offset one minor problem - aircraft carriers mostly carry air and are thus not very dense. Submarines rather need to have a relative density to the water of about 1.
RP1