#dc, 96 bytes

?sbsa2sf[q]sk[lalf~lblf~szrlz+0<ksbsale1+selsx]ss[lfn[^]Plen[ ]P]sp[0selsxle0<plf1+dsflb!<w]dswx

It reads one line of standard input. Its output does not end with a newline. Example:

$ echo 301343045 421880263 | dc factorize.dc
1021^1 59029^1 $ 

Code with comments:

# dc(1) is a stack language, like Forth. Programs push values on the
# stack, then operate on them. For example, to calculate
#  (2 + 3) * (9 - 4)
# the dc code is
#  [2 3 + 9 4 - *]

# [?] reads a line of input.  We expect two integers >= 2.
# [sb sa] stores the integers in variables.
? sb sa     # a, b = two integers from input

# This program sucks common factors from a and b, looping for
# f = 2, 3, 4, 5, and so on.  This method only sucks prime factors,
# but wastes time when f is not prime.
2 sf        # f = 2

# Code in [...] does not run until the program calls it.

# k = code to break a loop
[
 q           # [q] breaks two levels of [...]
] sk        # k = break

# s = loop to suck factor f from a and b
#  This loop increments e, the exponent for factor f.
#  Please set e = 0 before entering this loop.
[
 # [la lf] puts ( a f ) on the stack.
 # [~] does division and remainder.
             # STACK:
 la lf ~     # ( a/f a%f )
 lb lf ~     # ( a/f a%f b/f b%f )

 # [r] swaps the top two stack values.
 # Hold z = b%f and swap a%f with b/f.
             # STACK:
 sz r lz     # ( a/f b/f a%f b%f )

 # f is a common factor if a%f and b%f are zero.  Because a and b are
 # non-negative, a%f and b%f are zero only if a%f+b%f is zero.
             # STACK:
 +           # ( a/f b/f a%f+b%f )

 # Call k to break loop unless a%f+b%f is zero.  [<k] conditionally
 # calls k if the comparison is true.  Comparisons in dc are
 # backwards, so [3 0 <k] would check 0 < 3.  Because a%f+b%f is never
 # negative, [0 <k] is golf for [0 !=k].
             # STACK:
 0 <k        # ( a/f b/f )

 # f is a common factor, so suck it!
 sb sa       # a = a/f, b = b/f, STACK: ( )
 le 1 + se   # increment e, the exponent for this factor
 ls x        # continue loop, [x] executes s
] ss        # s = loop

# p = code to print "f^e "
[
 # [n] prints a number without a newline.
 # [P] prints a string.
 lf n [^]P
 le n [ ]P

 # DEBUG: Uncomment to print a and b.
 #[(a = ]P la n [, b = ]P lb n [)]P 10P
] sp        # p = print

# w = loop to iterate factors
[
 # Call s loop to suck factor f from a and b, and set exponent e.
 0 se        # e = 0
 ls x        # call s loop

 # DEBUG: Uncomment [c] to clear the stack.  Loop s leaves two junk
 # values ( a/f b/f ) on the stack.  Deleting [c] for code golf saves
 # 1 byte but leaks junk on the stack.
 #c

 # Print "f^e " if 0 < e.  Comparisons in dc are backwards, so
 # [0 le <p] would check e < 0, [le 0 <p] checks 0 < e.
 le 0 <p

 # Increment f.  [d] duplicates top value on stack.
             # STACK:
 lf 1 +      # ( f+1 )
 d           # ( f+1 f+1 )
 sf          # ( f ) as f+1 becomes f

 # Continue loop if b >= f.  This is golf for f <= a and f <= b, as
 # extra iterations of the loop cause no harm.
             # STACK:
 lb          # ( f b )
 !<w         # ( ), continue loop if not b < f
] d sw      # w = loop; STACK: ( w )
x           # enter loop unconditionally; STACK: ( ) at entrance