You can use facet.limit
to change the number of returned values. Set it to -1
to make Solr return all possible values for a field and not just the top 100.
&facet=on&facet.field=txt&facet.limit=-1
You can also use f.txt.facet.limit=-1
if you have more than one facet and just want to change the value for that single field.
You can also use the Terms component to retrieve the tokens indexed for a specific field - depending on your use case it might be more efficient to use the terms component instead - you'll have to evaluate the performance for your exact use case and setup.